Korg D1... Operating it couldn't be simpler.
Very good AP en EP sounds, layering strings on top of that is a question of holding one instrument button down and pressing the other you want to layer, with one hand, no problem. Removing the layered sound is just as easy.
Based on the manual, the D1 would work pretty well, with one slight kink. Remember, the OP want to be able to bring in strings under his choice of piano, Rhodes, and Wurli. So every time you turn on the D1, you'll need a few button presses to turn the EP2 button into a Wurli (since Wurli is in Bank 3, and the system defaults to all Bank 1 sound whenever you power up). If the piano, Rhodes, and strings sounds he prefers aren't Bank 1 sounds, their respective buttons will have to be defined to their preferred sounds as well. But after spending maybe 10-15 seconds setting up the sounds you want, real-time switching among those three key sounds (with or without strings) should work quickly and easily. But I'd still rule it out for topping 35 lbs!
It’s hard to think of an 88 key DP that DOESN’T meet OP’s requirements...until you get to the question of weight.
I initially had the identical thought, but there has been a move lately for some of the basic DPs to use the keys themselves to select sounds (some of the lower end Casios, Rolands, Kawai), so I think that would be awkward for changing sounds while playing. Some boards have Registration buttons to easily recall your most commonly used sounds/combinations, which helps, but even then, there may be only four (or four available at a time, in banks), which isn't enough if you want easy switching among essentially 6 sounds (piano, Rhodes, Wurli, and then those same three sounds again except with strings added). And I'm not sure that the boards allow you to smoothly change sounds using Registrations, of if a held piano chord would cut out when you switched to the "with strings" variant. So as I thought about it, I realized there were some complications... which is why I ended up suggesting the boards that I did, that I thought could probably actually do it most easily.
Thanks all. The D1 might be the best fit, but 35 pds might be a tiny challenge for me. And about $1k is my max budget, so the Korg appeals.
Check the other boards I mentioned, all at least 5 lbs lighter than the Korg, almost all under $1k.
Might just have to stay with my old Privia though.
Which Privia do you have? (Lots of Privias do have a way to do what you need... but then maybe the issue is still that you're not satisfied with their particular piano or EP sounds.)
A lighter weight Korg at 25lbs is the B2, cheaper in cost and more basic in inclusions
No layer function, AFAIK.