IIRC the limit on silver production only exists in the Stonehenge tribunal, but I might be wrong here.
Change this for "I will create the oriflame for you" or "I will make a sword that will make you and your kids immortal in the battlefield" (70 year duration, but you do not have to tell him the details about that) and there you go. you can probably get away with a fairly cheap price for a chunk of forest in a difficult to access location. The fact that you can "act geomancer" and construct a Roman road through said forest is totally secondary when you negotiate.
I have no problem with your situation. it looks ripe to generate stories both in the physical and moral confluict. Will you sue your goetic arts to save your friends? Will you renounce goetic arts to be good? And normal magic? Ain't that the same? Will you want to manage the inheritance since you would do better than your lousy cousin that is exploiting the commoners living there?
Sorry I forgot that there was a bit of YSMV there - I've loaned my corebook to a player who is working on his magus.
What I've told my players is that everyone more or less sticks to the 20 MP of silver limit of the Stonehenge ruling because if they don't, they might end up with a more restrictive ruling in their tribunal - we're in Provencal.
IMO, direct conversion of vis to silver is a bit of a waste. Ars is the game system that wants players to ask themselves why they are doing something. For grogs, it's easy, because the magus told them to. For companions, it's more complex, but it goes to the magus needs it, and looks like it might be fun, sure, why not. For the magus it's a complex decision matrix based on what the magus's goals are. Magi can have any goal they want, and can probably accomplish any goal they set within the game. What do your players want to do with their magi? Being new to the system, the questions are probably more about how than why, but you should be nudging them towards the why...
