Dude, you asked to let you know what I think and I'm gonna be honest with you: probably I'm not the kind of person to ask an opinion about these styles of maps; I simply do not like long infuriating trials. I made it through the first floor of the first trial and it took me a minute and a half, there's 5 more of these, it would take me 12 minutes and a carpal tunnel syndrome, and as far as I understand, it's only a half of a trial, so double it and get 24 mins, and you plan 10 of 'em! So 240 minutes, it's a 4 hour run not counting fails. I don't think someone possibly would beat it. And I don't understand unbeatable maps - I've attempted Skinny Dip for two weeks, learned to get through floors 1-3 consistently, but then dropped it. I'm not that kind of player.
HOWEVER!!! I really, really dig your concept of interconnected trials, and hub architecture, and I would be sooo madly glad to play something like "rule of 4" with lesser and smaller bite-sized trials so more people could beat it and there will be competition on the best times.
AND I really dig your organized structures, and patterns, and style; particularly in the hub and mountains map. So my advice (if you need it) will be to try and make a shorter map that you yourself will enjoy to drive and complete under a minute and people will absolutely love it.
Tbh the whole point of Rule of 10 isnt to beat it. That was how girth was going to be, but then @PonkFreud changed that. I dont actually do a whole run-through of my levels for the same reasons as you, (I've messed with Girth a little but mostly segment testing) but I make stuff like the Rule of 10 project specifically for the maniacs committed enough to beat it. Ngl i might make a micro rule of 10, definitely with the same style hub since I'm also really impressed how it turned out when i did some flow testing. I might make some shorter maps, perhaps some speed tracks, so yeah be on the lookout for those! Again, thanks man for takin the time to type out all of this, and i will absolutely take up your advice! :D