forget about feedback, guys. Feedback in analog is some unpredictable serious fun, but...in digital it is mayhem to code and each device inside a loop would need to cope with it in very special ways. Or you have delays in each backlink, no way around it. OK delays in backlink can be useful for mayhem delay with anything in feedback loop, much like the filters in the multitap delay, but nothing else.
For routing...I already do spaghetti with sends in the inst.fx. It is something to wrap the head around, but it works nicely for me now. I could well imagine having sidechaining aka multiple input/output effects in there. Sidechaining like vocoder or ringmod or sidechain comp, or also like the bandsplit with multi out - maybe with receive devices, or pointing to another multi in, but then there would need to be some visual feedback.
The limitation of left->right and top->down is kind of...ok for me. I know this is to prevent any glimpse of backlinks by usage interface limitations, but it already works for me.
I could at no point get around to having a single track which contains multiple threads of processing. C'mon, joule, anyone but the inventor is going to think its just plain artificial masochism! You're automatically bound to loose any kind of overview at the point where your processing involves more than say 7 devices at 3 threads. And I do usually use a _lot_ more of devices in my more complex inst.fx setups, and would also like to do more complex shit with them when splitting and combining devices would finally be available. And I'd HATE crawling my eyes to and fro inside that one...single...effect...lane...that works like...spaghetti...code? Instant despair guaranteed....
My take on this has for quite some while been to...make doofers work like the instrument fx, with multiple parallel lanes, and multiple inputs and outputs for the whole device... Somehow, but this way each thread would be at one line of visual execution. You could make sends (or general inputs) point to the additional channels of sidechain plugins, and make multi-out plugins point their channels somewhere like sends, have the whole multilane doofer have multiple outputs that work like the bandsplit plugin, all dandy, and no need to break the left->right top->down paradigm in all this. Just the sidechain extra channel sends would need some visual feedback to keep overview of the more complex routings.