I disagree. What you have shown makes perfect sense.
- You can put 2 parts on one stave in different voices (but don’t cross them much) - players will interpret as divisi, but to be clear add div. and unis. text. If the rhythm is the same, you can use chordal notation and mark it div.
- If they cross a lot, or are very different rhythmically, use divisi on separate staves.
- For special divisions (solo + the rest, back desk + the rest etc.) use a custom division on separate staves.
There was an interesting thread on string divisi