Any seasoned administrator has played around with business processes, record types and page layouts.

So I bring about this question; a use-case:
A user has 2 sales process, thus 2 opportunity record types assigned, lets say RT1 and RT2. While RT1 is the default record type for this user, he can choose between RT1 and RT2 wile creating the opportunity.
Requirement: The user should only be allowed to create opportunity with RT1, while he should be able to change the record type to RT2 when the opportunity stage changes to YYY.
How to perform this?

If I disable RT2 for user through the profile settings, the user can no longer change the opportunity record type i.e. he doesn’t see the option to switch to RT2.

My immediate option that works like a charm: To create a validation rule to not allow record type = RT2 for ISNEW record.


Alternative approach:
Can I create a custom button that open the new record URL with a parameter to set the record type?