>Convincing distributors (other than Gentoo, of course) to support this ABI
Surely it is application developers rather than distributors who would support this thing?
In the Gentoo case, presumably I'd merely have to remember to pick a kernel option before emerging something that could use this. Said option would be mentioned in the middle of a 300 package emerge, after setting a USE flag, which I'd never notice 8)
For now fixing how CUPS can cause a 2 hour load time for a Libre Office file is probably going to yield better performance improvements (its something to do with printers being unavailable away from "home")
I am not an expert but this look like a bodge of some sort. An application is written to work with a 2^n bit system. If it runs on a 2^n bit system then great. If not then you'll need a compatibility layer.
Surely the 64 bit version of a (previously) 32 bit app can be efficient in terms of memory and register usage.
I can't help but be reminded of the 16 -> 32 bit migration.