he's gonna be running a vf30, no need for a BOV. if you HAVE you get one because you want to run 22 psi on a vf30 then get a sti recirculating valve.
As long as he isn't an idiot, he should be fine with a vf30. The people that breaking stuff with 250 whp are probably the same type of people that break stuff with the stock turbo.
Get a good tune. That would be the only thing that I splurge on. You can get a used VF30 and pinks from a reputable vendor on these boards for cheap. That's all you need (aside from the fuel pump).