try and get the sound you want to achieve by using asoftsynths internal filtering etc. abilities rather than trying to achieve those results by whacking a filter behind it. u have almost all the tools to sculpture your sound in those synths themselves, use them :!:
depends if you like your soft synths filters I guess ... the rest of what you say is I reckon is spot on ... except


You can't polish a turd :!:
Actually, in techno I reckon you might be able to, just sometimes, actually polish a real turd ... We were talking about that in the studio the other day, not sure what the rules would have to be.

Probably you can frame the turd in any sonic context you like.

You may not turn the turd into something unrecognisably like the original sample.

Maybe no subtractive processes.

Need to find a good turd to start with.