As a compromise I will open up the pokedex to 251.
Well this changes everything! Sort of
If you're concerned about keeping it limited, you can probably just limit is to whatever's canonically found in Kanto way back in gen 2 plus or minus a few of your choosing. Throw in the occasional Johto native when we're battling an NPC, stuff like that. I mean if I remember correctly like Slugma and Skarmory were originally only found in Kanto? I get what you're trying to do so those are just some suggestions and reminders. Pokemon distribution is bendy so you have quite a few options
I apologize if this is less than coherent. I typed this on my phone while at the hardware store