I just decided I'd go for a normal playthrough without any fancy rules but it almost turned into an unintended mono Ground run. My final team was
Torterra Lv 51, Drifblim Lv 49, Gliscor (MVP) Lv 52, Hippowdon Lv 50, Quagsire Lv 51 and Drapion Lv 50. But by the time I picked up on how many Ground types I had, I got too attached to Drifblim to slot it out for a gimmick (despite it being the weakest link tbh) and I really wanted to try out Drapion.
I did play on set mode though and it made the Ice gym especially pretty nasty, I had to cross fingers for Blizzard misses from Froslass to get through with Drapion and Quag.
Sinnoh itself was incredibly comfy to revisit, I was surprised by how much I still remembered about the game or specific mechanics or changes from later gens but I guess you don't unlearn this stuff this easily

The dreaded Gen 4 engine or HMs weren't that bad, I got by just fine assigning each mon one HM except Cut at the beginning where I used a slave briefly (Bidoof Lives Matter won't like hearing this).
The biggest grievance was probably Team Galactic. I generally never liked the evil teams for how intrusive they get with the pacing and boring grunt battles but it was especially bad here where I had nothing to quickly get rid off the
many Golbats and Bronzors spamming Confuse Ray

It actually gave newfound appreciation for Team Star in S/V who didn't slow the game down as much.
But the finale was great, I was several levels under the E4 and Cynthia and they all put up a solid fight except for the Ground member ironically.
Hippowdon's sand Glscor's Sand Veil made for a nasty combo that cheesed a good part of the Cynthia battle until her Garchomp came in and hit its Dragon Rushes without any issues

Good thing I had Ice Beam on Quag.
All in all this was a really pleasant nostalgia trip and if I get around to replaying one of the 3ds games (I have not touched any of them since release) I'd like to do an actual mono type run with either Dark or Ground.