Did you have a look at my dub delay here? – https://godlike.com.au/index.php?id=420 This has independent left and right delays, as well as filtering on the feedback path. I’m looking at adding a second delay line, and second input for adding special effects into the delay loop and adjustable left/right crossfades on the feedback loop, as well as an envelope follower. I could probably add some LFO’s as well, but as it is it probably ticks a few of your boxes.
…this I have downloaded and checked… would be a good starting point for some adds..