What I propose is simpler, and, if I am not mistaking, would be a simple variation of the existing fluid engine. I could even be considered like a fix.
Oh, I'm not proposing to wait for my project to be released; that might take quite some time or even not happen. And, as you say, it is a big redesign that almost certainly will not please everybody. So indeed fixing FluidSynth would be useful.
Do you (or anyone else) see a problem with the solution that I propose ? If not, I'll try to implement it...
I can't see a problem, other than implementing your solution might (or might not) require bigger changes than expected.