Hmm, what about something more generic? If you exactly stick to instances for every LightSelect element, then try the attached experimental (and badly/quickly written) startup script. It would
- go through all LightSelect render elements
- get all instances from the lights already there
- add those instances to the LightSelect element
automatically every time you either open render setup or start to render. Of course you could do something similar as you mentioned (hotkey/button).
There is no wrong and right when in comes to light sources in LightSelect elements, there are just very different requirements. So I cannot imagine a perfect, generic solution as well. But the script may give you a direction to continue, it works a bit as if there would be a ticked "Include instances" checkbox in the interface of the LightSelect render elements.
Good Luck
Thank you so much mr Frood!
I will give this a go and report back to you.