I agree with you on the region design, though I wouldn't call it a problem with the series. BW2 are some of the best games in the series and yet have very linear region design. After replaying RBY I would appreciate them to take another stab at nonlinear regional design though. It's a nice feeling to have a lot of options, which is something you really haven't had in terms of main story progression since gen 2.
On dungeon design, well I'm kind of 50/50 there. Mt. Moon I would classify as a long, grueling dungeon early on but it's mostly because you have so little at your disposal at that point. Mt. Moon also has a lot of wrong paths but you can find rarer pokemon (Clefairy, Paras) and items in the wrong paths making it worth it.
Rock Tunnel on the other hand just sucks. It's just a series of forks in the road where one way is progress and the other is a pointless dead end. FRLG addressed this somewhat by putting items and a move tutor in the dead ends but it's still a lame dungeon overall. I do appreciate that this and Mt. Moon force you to actually use your potions, something I barely ever find myself doing nowadays, but I wouldn't call it good dungeon design.
Give us a huge, maze-like cave with worthwhile rewards at the dead ends and with more unique ways of splitting up the paths. For some examples, I think gen 5's victory roads were pretty good at this. Especially BW2's victory road, which had like 5 different paths which intersected at a central area, one of which you started at depending on your version, and 3 of which eventually intersect again at the end of the dungeon. And if you explored every path you could find some secret areas with tougher battles vs. high level veteran trainers and TM rewards. I want more dungeons like that.
On the safari zone...nah. Safari Zone is just obnoxious. I do miss when some pokemon were rarer than others, but Safari Zone is not the way to do it and wifi trading ruins that anyway. And I'd rather they keep their online features than have some pokemon be rare or special.
I'm guessing you're playing Blaze Black? That's not a thing in standard Black.
The only double gym leader battle in the series in Tate&Liza from RSE.
On dungeon design, well I'm kind of 50/50 there. Mt. Moon I would classify as a long, grueling dungeon early on but it's mostly because you have so little at your disposal at that point. Mt. Moon also has a lot of wrong paths but you can find rarer pokemon (Clefairy, Paras) and items in the wrong paths making it worth it.
Rock Tunnel on the other hand just sucks. It's just a series of forks in the road where one way is progress and the other is a pointless dead end. FRLG addressed this somewhat by putting items and a move tutor in the dead ends but it's still a lame dungeon overall. I do appreciate that this and Mt. Moon force you to actually use your potions, something I barely ever find myself doing nowadays, but I wouldn't call it good dungeon design.
Give us a huge, maze-like cave with worthwhile rewards at the dead ends and with more unique ways of splitting up the paths. For some examples, I think gen 5's victory roads were pretty good at this. Especially BW2's victory road, which had like 5 different paths which intersected at a central area, one of which you started at depending on your version, and 3 of which eventually intersect again at the end of the dungeon. And if you explored every path you could find some secret areas with tougher battles vs. high level veteran trainers and TM rewards. I want more dungeons like that.
On the safari zone...nah. Safari Zone is just obnoxious. I do miss when some pokemon were rarer than others, but Safari Zone is not the way to do it and wifi trading ruins that anyway. And I'd rather they keep their online features than have some pokemon be rare or special.
18 would be a bit much. I'm cool with trainers joining you, but I can't see it working in a solo run other than how they did with Generation V where occasionally you'll have a trainer participating in a doubles battle with you. Also with Gen V I find it refreshing how all the gym leader battles are two on two in Black 1. It's different and I like it.
I'm guessing you're playing Blaze Black? That's not a thing in standard Black.
The only double gym leader battle in the series in Tate&Liza from RSE.