This was brought up before (maybe even by me on the old forum). I originally thought that if you had Puissant Ability Parma that it wouldn't increase your Magic Resistance, but would be useful in Certamen for example. With the wording of the errata however I'm not so certain.
"You are particularly adept with one Ability, and add 2 to its value whenever you use it. Note that you do not, in general, use an Ability when learning it, teaching it, or writing about it."
With this wording it seems logical that a beginning magus could have the equivalent of a 3 Parma. What do you think? Or maybe you could just point me in the direction of a previous thread that answered this.
It was my understanding from conversations on the Berk list that this was the intent (level 1 parma acts as level 3) and was actually the reason behind the errata (although it could have been the vis use limit as well). There may have even been a quote from David to support this but I'm unwilling to put so much faith in my memory that I would encourage you to count on it.
I don't think that this would be unbalancing. Does anyone else forsee any problems with it?