Hello @deven
at the moment we donāt have a way to enforce a validation like the want you need. We have this feature request: Custom validation that you can upvote that could solve your problem down the line. Itās something that we believe should be done, so it might be added at some point.
Meanwhile, the only idea that I have is to use modular blocks instead, where you can limit the type of blocks that you can add, so you can have āfirst level menuā and āsecond level menuā blocks and you can limit it this way.
Itās not the same as using a different model, but maybe it can solve your issue?