The base install adds eight entries, the optional content an additional one. I can mitigate the optional one (sparring circle) with a level model replacement, although that merely makes for a different type of potential incompatibility.
Diversified Wounded Republic Soldiers On Taris currently adds twelve of its own, but a number of those are "spares" that I was toying with swapping around with scripting before this issue cropped up. I'll have to revise that and remove the unnecessary ones. In fact I was already replacing the room model in that instance anyway, so maybe I could just dispense with placeables for this one altogether and make them part of the room model. That will probably mess up my staggered animations though.
It looks like vanilla entries 8, 9, 47, 62, 78, 90, 94, 97, 115 could all be repurposed by K1R or some other major mod. I dare say there are a few more that are populated but unused in the game.