Hello everyone,
I like the concept of the "Mental Construct" lab flaw presented at page 120 of Covenants and I want create an item with the crown of hermes effect (described in the box at page 121) for my magus.
It is stated that a magus cannot use the lab to bond with familiar, enchant items or Longevity Rituals without sophisticated magic.
Well, I'd like to develop some of these sophisticated magics and include the lab activities above but actually I don't know from where to begin!
Any input?
You can do these only in a real lab. That's the sophisticated truth. 
Spend a 100 years painstakingly researching how to craft magic items with your mind, and your mind alone
Lament how much easier it might have been to just spend a measly 5 silver on a lab like everyone else ^^
Still, at least you'd feel suitably smug
Well, there is one other way...
Initiate yourself into the Dream Mysteries from TMRE. I thik this was you can take something from your dream-lab into the real world. Just like in the example given in the book with tears of a rhino.
This way you could produce something in the lab (like a longevity potion) and consume/use it in the real world. A dream of a potion!
Cheers
I have to remark I agree with the other limitations, but I find the No Longevity Ritual limit very very questionable, to say the least. Longevity Rituals for the self are very personal and inward-focused magical activities, and the ritual may be structured to involve little material props besides vis consumption, it needs not be something so gross as a potion, I do believe that the maga should be allowed to use a Mental Laboratory to create Longevity Ritual for herself.
Boasting before your sodales? It is priceless.
For everything else, there's the Mercere Exchange Card 
The Mystery of the Morphic gate was gong to be my suggestion as well. There's also no reason, (if the rules story-guide believes that it is a good thing) that you couldn't develop a similar mystery with a different theme that worked in much the same way and avoid the thematic elements of dream magic.
Another thought would be to create an item (or better yet, enchant your talisman) with a muto mentem(He, Te, etc) effect that changes the thoughts into actual items. Give it duration concentration, item maintains concentration and lots of uses per day and you can carry around dozens of enchanteditems in your head.
There is the problem of how to enchant the items in your intellectual laboratory. How do you get vis into it? Could a muto vim (me) spell do the trick? You might consider transferring the vis into your body using the rules on page 91 of the core book (be careful of the infernal stuff).
If you learn the art of memory and construct a memory palace for yourself, could you move items between the memory palace and the laboratory of Hermes?
My maga "simply" uses MuX(Me) to move things into her lab. Thus, her familiar has a MuAn(Me) effect to move it into her mental laboratory, and in principle MuTe(Me) should work well to move material things into the lab too (I'd ignore the other requisites, but you may put He variants and so on depending on your SG).
Regarding vis I had an elaborate plan to enchant an item with gather the essence of vis, a detect vis and type spell that makes sparks dance in the 15 gems according to how much vis of each art it holds, and a MuTe(Me) effect to turn it all ghostly. But that had as much to do with my maga's ascension into immortality in the Spirit Magic mysteries.
With a less generous SG, the dream mysteries seem the only way, and that too is doubtful.
On Mental Locations of Labs and Dreams: IIRC, dream travel to the memory is possible but tricky; for a character with dream mysteries, I think it would be very nice to have his lab and mental palace (if any) both be accessible through dream travel.