Here is where I disagree:
You walk into town and your formulaic spells have good chance and all your spont spells are getting 2 extra botch dice. You walk into a city and that is likely 3 extra botch dice. That is just for being in the town/city. You get near the church/castle/graveyard and it is now 4 botch dice. For some reason you have to cast in cathedral and that is 5 botch dice.
You are chasing after an infernalist and you manage to corner him in his lair, infernal aura 4 and to get past his magic resistance provided by his infernal familiar, you use 4 pawns of vis to boost casting total and thus penetration. You are now at 9 botch dice.
This ruling on rituals in calm situations doesn't help against either of those senarios. In fact that first one is fairly common that you have to cast in a crowded market or town because someone reacts to you negatively.
This is why gold cord, cautious sorcerer, flawless magic and mastered spells aren't cheapened.
Lets also mention that mastery brings with it special abilities like quick casting, subtle, silent casting, multi-casting, penetration bonuses (flawless magic means all your xp in master is doubled adn all spells start off mastered).
THen again, you are walking the covenant and something happens for an emergency (timmy fell down the wall again). You are now in stressful situation. That spell mastery means you can't botch in the magic aura with your formulaic spells.
These are all much more common situations than most ritual spells. Gold cord especially since a good gold cord means you can experiment with a +3 risk modifier in the lab and low and behold, you still only have the single botch die. Sure you can specialize you lab to be safer but with gold cord, you don't necessarily need to.
so the only one that this is really issue with is Mercurian magic. You claim it cheapens this virtue since using half vis is half botch dice. The point is that you are using half vis.
I don't know many sagas that every mage can easily have 10 pawns for a level 50 ritual at whim but getting 5 isn't nearly has hard. Not to mention that you get a free wizard's communion and even spell mastery to wizard communion raises its effective level so that you can do the higher level rituals easier.
My personal experience is 20-30 pawns a year of varying types among 6 mages. Take out 4-6 (let's say 6 for a nice aegis) and that is 4 pawns a year a magus. Getting vis for your rituals is not so easy and can take several years to save up. If your covenant doesn't have right type, you might be trading it at 2:1 to get the right type.
Paying half vis for your rituals is a huge boon.
Botching rituals is not a good thing and most of them should not be botched, especially if you take the time to master them. In fact flawless magic becomes that much more powerful since your rituals are all mastered that one important level.