Splitting divisi passages in staves

[YTG 1234]

Hello everyone,

I want to set divisi passages (for strings) in the part as separate staves, but in the score combined.

I am aware of the \partCombine functionality, but I'm not sure that it suits this use case. Precisely:

1. Is there a way to set a minimum length of time for identical notes to be merged in unison? That is, only if I have more than one continuous bar of unison do I want to actually set the parts as one voice.
2. Likewise, I don't want the automatic part-combiner to immediately say "SOLO!" when the other division has a short rest, but rather print the rest.
   
3. In the parts, how can I set unison passages using only one stave? I could make the other empty, but I don't know how that affects the combined part.
4. Not necessary, but could I set (even manually) simpler passages as single-staff polyphony in the part, but more complex ones in separate staves?

I've taken a look at https://lilypond.org/doc/v2.25/Documentation/notation/hiding-staves, and it seems useful, but I don't know if it can merge unison properly. Perhaps I can use this method in the parts together with \partCombine in the shared stave, and in the score only use a shared stave. Would that work? Would the Staff.keepAliveInterfaces changes mess with the score in any way?

But that still doesn't consider points 1-2 above.

Thanks for any help!