True, your mentem spell will but in the lab, the 5 intelligence vs the 2 intelligence is huge. In soak the 5 stamina vs 1 stamina is a large benefit.
Let's put things in perspective. Yes, for most skill use, the spell will outdo the high attribute. The difference between the 2 intelligence and 3 intelligence is like +1 to all your techniques or +1 to all forms. Between a 2 intelligence and a 5 intelligence is +3 to all lab totals and 2 stamina vs 5 stamina is +3 to all casting totals and also equal to two great charactistic virtues (we only get 10 virtues).
The high attribute is incredibly big for the following: Lab total (intelligence), Casting total (stamina), Soak (stamina), initiative (quickness for that fast cast), Quality for books/texts (communication), Load and what can be carried (including able to wear armor for soak, Strength).
There are few things more effective for the vis (8 pawns to raise a negative or 0 to 1, 12 for 4-5 seems like it mght be lot but for chargen, more than worth it. It is always harder to do this sort of thing in play it seems.Take a -3 in your initial attibutes, spend 16 pawns and suddenly it is -1, meanwhile you have +3 int and +3 stamina and equal of two improved characteristic virtues).
Especially for a magus in their first decade past gauntlet. The cost should be also way more than just the cost of the ritual, there is cost to be paid for getting it cast but that isn't set anywhere. The "I belong to cult of heroes of Mercere so they have mages that will do it for me" doesn't seem right.
Yes, I like a different flavor of play than you which is why I left Andorra, the player philosophy and game nature was such that it was not what I wanted to play. If I am a player here though, I am going to chime in these sorts of concepts.