Glad you're enjoying it!
The next update will let you pack, move and sell placed equipment so reorganizing your gym will be much easier.
For tracking gym clients' progression, I don't really plan to go further with that (unless I find a way to get better models with shape keys, or just a lot more models). But I will be adding hireable employees at some point: you'll be able to train them and they'll gain visible physical progression over time, with a screen to track their stats and body changes. Models will update the next day once certain stat thresholds are reached.