Tricky issue with alpha channel/blending modes/export

I've produced a short ident for a company which invloves blending modes over a black background. Annoyingly theyre now asking for a version with an alpha channel - to which I'm going to struggle as the 'transparency' is effectively baked in as a blending mode.  The growing roots is essentially just an auto filled vector which repeats 4 times getting darker as as to look as though its disappearing. If I remove the bg layer (as you should be able to see) of course I lose the transparency effect from loss of blending mode. Any tips on how to get around this? I imagine trying to remove the black in the final rendered video would look awful.