How about AF?
Well, while you're getting a 35mm system - why not get AF as well - that way you will have something that has a different sort of use from your MF gear and not just in terms of size. I'd say an N90s or maybe even an F4 would be nice with a 50/1.8 AF to start with. Although I use my N90s only with manual lenses, but that's just because 35mm is still my primary system.
But whatever you get, I'd say it needs to be complemented with a lightweight 35mm rangefinder. The Olympus ones are great the RC is light and manual but the XA, even though it's A-priority only, can't be beat for compactness!