I wonder, is it really the wheel base which makes the car more twitchy? It will be a factor but I expect the wheel geometry to have a bigger impact. Front wheel alignment, caster, camber, scrub radius, that kind of stuff.
A shorter wheelbase was always on my wish-list for the '86; never to be, of course. While it's doesn't currently have the bus-like feel of the very-long wheelbase of my old 325ti, it's still longer than I'd like.