With the newest update, it is possible to attempt Classic with only the 9 generations of Starters, with base 10 IVs and no moves. I haven't yet succeeded in a full attempt yet (I only got to floor ~115), but I'll keep up the attempts.

As for supplemental rules, I can suggest some, though they may conflict with the existing ones:

Time can start at choosing Yes, after Starter selection and before the first battle. Time can end at Magnificent message, post final boss defeat.

You can catch and use Pokemon - in fact, it's likely mandatory to even complete the challenge.

Running is allowed. Refreshing of battles is disallowed.

File setup is likely pretty uniform for everyone, with 5x speed, no animations, etc. but runners can use what's comfortable.

Category has been made by the way.