I just tested nirnroots in game. I checked that nirnroot roots are deleted and checked the code after decompiling nirnrootactivatorscript.pex and defaultdeleteselfonreset.pex.

Now both glows and roots are set to deletion on cell attach, while nirnroot generates new instances of them on the same event.

I won't change "possessive corpses" as this part of the mod is optional, won't conflict with 1.6 fix and support previous versions (besides adding different options for nirnroot's behavior), but you'll be fine not using any third party fix for nirnroots. Now vanilla handle them fine.

That is good news indeed. Thank you very much for your efforts in looking into it.

Yea I'm glad it's sorted. Still going to use Mart's Debloatifier, just because it's Mart