I think you missed my edit - limiting any feature explicitly to any mode is a ridiculously stupid idea IMO.
I did miss your edit, thanks for pointing it out. There was a time when I would agree with you, but as someone else highlighted earlier in the thread, we have missions now that encourage farming NPCs - FDev didn't design the game that way (imo) but it's how many players approach it, so they adapted & added content in-line with how the game is actually played.
I don't see this as any different. There is a demand for a solution, it can be added. If there were sufficient demand for a solo only layer I'd support them too. Power Play is effectively a different game, played in parallel with the existing one, sharing assets & in a shared environment. The Alien content is another layer, gated by distance. Wings are multi-player only content too, so while I understand where you are coming from I don't think FDev are so firm in their opinions on this as you.
Yes the BGS will remain available for all, but there is no reason why a new layer couldn't be Open specific, and PvP specific.