imo get a new "regular" mechanic - he sounds like an idiot and if he isn't familiar with evos then why would you trust him?

no risks as long as you or the person installing them knows what they are doing, which at this point I'm thinking your at a major risk of failure

 

Only downfalls to cams that I can think of are (not including installation errors):

Rough idle (can be tuned out)
Loss of vacume
Random low idle/stall
Some say the reduction in vacume compounds BPV flutter on some cars.

Would I remove my 272's? Hell no!