Charles, after reading most of this thread, here are my thoughts on de-GASing:
1) Don't do Pentax, since you already have Olympus and Minolta and Nikon. Penatx co-developed their coatings withe Zeiss, back in the day. Zeiss T* = Pentax SMC.
2) For a lightweight, sharp kit, the slower Zuikos are very good. My kit is 28/3.5, 50/1.8, 135/3.5 and 300/4.5. All are sharp. One thing to remember with the Zuikos is that the early ones were not multi-coated, so they are more susceptible to flare, and minor flare is just lost contrast. Lost contrast is often mistaken for lack of sharpness. The key with them is to almost always use hoods. I have an RMC Tokina 75-150/3.8 (fixed) that is very good too, and that could replace 85, 100, 135 mm lenses in your bag.
3) Maybe it's time to take your Minolta MD kit out for a spin? I always liked them, back in the day, and the lenses are great. IF it doesn't satisfy, now's a good time to move them on, as they're going up in value with the film renaissance.
4) You mentioned your old eyes having a hard time nailing focus. I found that while the tactile experience isn't as good, my results are better with my Nikon AF stuff. The Nikon N80 body is about the size of an OM1 but with the bigger grip. It's very light and quiet; wonderful shutter. (and as an OM owner, that's saying a lot) I have a small set of lenses for Nikon AF that are good for walk-around duty: 50/1.8D, 28-105/3.5-4.5D, 75-300/4.5-5.6 (pre-D) and a Tokina AT-X Pro 17/3.5. When you want to go light, just bring the 28-105 on the body and the 75-300 in a small bag.
5) Get rid of those European cameras and lenses while they're still worth something. (repairmen who will work on them are a dying breed) If you really want to keep the (heavy) Zeiss lenses, a Yashica body is a good option. I had an FX-3 Super back in the day, and it was fine. Not as satisfying as a Contax, no doubt, but it will mount the Zeiss lenses. To me, this is silly though, if you're trying to de-GAS. Sell those couple lenses and re-invest in the one system you will stay with.