Should for you: no hermetic gestures, be a restricction? ( Major hermetic flaw)
You are privated of any bonus by bold gestures.
And hermetic cast? The same with voice
No bonus x loud voice
+
You must roll Per + Con each spell R: voice
Does it mean that you must always have the no gestures penalty to spellcasting as well?
GOod point. But then maybe part of the story would be to develop new gestures in the same way one might learn to cast in Greek.
I like this idea a lot. Not enough to play it personally, mind you, but still a lot... 
Of course!
Well unless you have subtle/quiet magic but anyway you lose flexibility.
Hedge wizard is waiting for you next corner
Questionnable, IMHO, particularly if the player takes tha Subtle Magic virtue. This would allow minor virtue to counteract almost all of the effects of a major flaw.
Major flaws should inflict a more severe effect than a simple -5 penalty. Restriction should prevent you from casting in circumstances that are sometimes out of your control. I'd be fine with a Restriction that would force the magus to always use gestures.
Just my 2 cents.
I would count this as a minor flaw, not a major one. Since it applies to casting problems it grants you a minor flaw status. Otherwise it would be simply a quirk with V&F implications.
A major flaw should not be so easily mitigated. As described, this flaw can be mitigated by something as simple as 5 xp in spell mastery ability.
This is closer to a Necessary Condition, because it is relatively common and it is something that the magus must do for his magic to work. Restriction can be like a necessary condition, or it can be the state of the magus, the environment and it should be relatively uncommon.
I'm not so sure about this:
Then, the flaw which stops your spell and magical effect (bind magic in HoHTL , mercere section IIRC) is not a flaw, because your character doesn't care what happen after he is dead (you stop playing that character anyway), or the flaw "waster of vis" is of no importance for someone who never use vis or even blind if you have appropriate intellego imaginem magic. Or cripple if you are able to use ReCo spells.
But, for a fact, I would say "restriction : speaking" which prevent you to use words (-10, overcome with 2 minor virtues) and range "voice" obviously, is ok. The two in the original post are not something I would allow as restriction, not because they are easily countercarred flaws, but because I don't feel them right in the Ars setting.
Perhaps, but Bound magic is also an alternative gateway to taking of the Mutantum magic virtues, without being a mutantum magus. Additionally, if your a Merceris magus, having bound magic is really bad since no Redcap really wants to buy an item from you, nor will the House contract with you for items, or if they do the character with Bound Magic is the last choice possible
But vis is almost always used, at least once, most importantly with one's Longevity Ritual. The implications of which can seriously impact how old a magus can grow to be. The characters who use magic to overcome blindness, or being crippled might also cause warping if they are used more or less constantly. Relying on magic to overcome Flaws isn't free.
If you are a waster of vis don't be a longevity specialist.
I never even came close to stating that was what was happening. Point is, even a Waster of Vis needs a Longevity ritual. Or might need to or want cast other rituals. Or might want to boost penetration on a spell in an emergency. A Waster of Vis will generally avoid these situations which suggests that the flaw is working, and forces the character into different avenues of interest/ability.
I agree, but expending XPs on masteries you wouldn't have needed otherwise is not free neither. Isn't it?
You got me there.
5 xp to get rid of gestures is not equal to the 15 xp needed to get rid of hermetic words. So, the entire premise is asymmetric, and needs work. And if one took Flawless magic it becomes 0 xp for gestures and 5 xp (doubles to 10) for quiet casting. And Flawless Magic is already the most powerful virtue in the game (IMNSHO). And who is to say that one wouldn't spend XP on those masteries, still and quiet casting are very useful mastery abilities, in their own right, and this flaw makes those abilities even more valuable and likely to be chosen.
It's a tossup, but like you've said there are other issues with the flaw as it has been presented here.
Let me rephrase that: anyone except a longevity specialist should hire a longevity specialist to do their longevity rituals. Only longevity specialists should perform longevity rituals. Hence, the longevity ritual issue won't really effect the waster of vis as long as they didn't try to specialize in that one area. The ritual issue, the need for penetration, and the like are actually going to need to be avoided.
In a perfect world, yes. Sometimes that isn't possible, based on the structure of the saga.
Great! Your anwers gave me a seasonable idea
And what if you joint 2 in one!?!?!
Restriction: no hermetic casting (cannot use neither words or gestures)
You need 3 minors to "override" & you lose the rigth of +1voice +1gestures & you lose the voice range unles you roll Conc...
Certainly a bit more crippling than waster of vis 
( that with a personal vis source...)
I don't remember if someone brought that up, but there is a minor virtue (HOHS, ex misc chapter?) which allow you to cast spells without hermetic casting. You still do a casting thing, but it's not hermetic. Thus, it would completly override the restriction you propose.
Sincerly, I think a restriction should not be something depending on "educated concept".
What I want to say is:
- restriction 'birds', ok
- restriction 'in water', ok
- restriction 'during night' ok
but restriction 'during holy days'... doesn't feel thematic. How would magic Know that you are on a holy day? what does it even have with magic!
restriction is a flaw related to the gift, since it's an hermetic one*. Thus, IMO, it should be appliable to anyone choosing to have it... even if they don't have hermetic powers!
([size=85]* yes, it's a bit sad that hermetic flaws are so called but relate to the gift. Counter intuitive for what I wanted to say here ^^[/size])
Your restriction only applies to a hermetic caster. What if a viktir (from TMRE) , with the gift, has a restriction and choose that one.
In fact, when I read the flaw, I read "these might refer to your state, such as touching the earth directly or having no beard, or to the target, such as birds or glass, or to your location when you use the magic, such as on a small boat or in a storm.
I read here "natural facts", not socially defined one.
But, there is more: "the restriction also applies to effect generated by any enchanted items you create". How would that restriction even come in play with items?
But if you and your troupe find it's okay, then it's okay. Bypass all those forum users who discuss to no end any question submitted to them!
(I agree some combination of flaws are just useless (in the sense that a flaw should mean a better story byt giving obstacles to overcome by other ways) and attempts of minmaxing under the coat. Why would you take "waster of vis" if you also choose "rigid magic" (no vis), and are not a magus who would ever consider doing items.)
I do not agree,
To me its a very nice flaw, possible inherit from a tradition, or by parens ineficacy .
If i look if i "roll per+awa" i could find flaws bind to traditions as could be hermetic or watever
Sure, but minor or major?
I'd be fine about it, as a minor flaw mind you.
Were proposed as major flaws.
Now i see that even the combination of both can be override ( somehow ) by 3 minors even having sequels and forcing a minor flaw... But you need to spend 3 virtue points to override.... 
Even vis waster you can dribble it with personal sources of vis... And blattant gift with Mu-Me/An spells... & cetera.
I dont know how to feel about this proposal...
Without treat about is killer... treated it is not...