You ever try to change an MD's outlook on anything? That's why I suggested making sure he can deal with a long hard road to solo before getting him into a twin for ab initio training.
Of course, it turns out this guy has already soloed in a 152, and the question is whether the first plane he buys (not the first one in which he trains) can be a twin, and the answer is, of course, "yes." But I'd still take him up through a the steps, say, the 152 he's flying to a 172 to a 172RG in rentals and getting his IR before buying a Bonanza or a Baron.
That's why I advocate coming at it from the other side and getting them to full functionality/capability ASAP even if that means extra time flying 2 pilot. For someone who has more money than time, this provides them the greatest value for their aviation $$$.
As for "stepping up", sure, while he's finding a plane to buy keep flying other stuff, but as soon as he has a plane, all time should be in it.