A low deck wedge seems fairly easy to accomplish, especially if you use the RB main bore. That saves you from having to design new main caps. There aren't a lot of low deck intake manifolds but perhaps if a block was available someone would step up with some killer intakes. If you stick with the RB main size then you avoid the low deck main bearing issue and you consolidate demand for RB crankshafts. Seems like a winner to me.

A low deck Hemi could be complicated by the pushrod angles. Might want to mock that one up and see if everything clears everywhere before you get too far into it. It seems like the pushrods already get into the cylinder bores at the RB deck height. If you lower the deck then the pushrods are going to lean over even more.