In general, forcing tags are a bad idea. With the exception of the required tags on meta, there are no forced tags anywhere. The Meta forced tags work because 99.999999% of the questions fit perfectly within one of the 4 required tags, but on all non-meta sites, the scopes of the sites are sufficiently broad there is no way to come up with a set of tag that can be guaranteed to cover virtually every question.
Dependent tags have the same problem. To paraphrase myself:
- Isn't it possible there is a generic SQL question that doesn't need an implementation tag? What is this user supposed to do? Add an implementation that isn't applicable just to satisfy this requirement?
- What if a new implementation comes out? Someone now has to remember to add the new implementation to the acceptable version tags. And if a question comes up before someone does this, how should it get handled? New users can't create tags so users may add a wrong implementation tag just to ask their question.
- To correct the above issue, you give users the ability to suggested required tags. Who us going to be responsible for approving user initiated changes? And what if a bad required tag is suggested?
While it does help limit the "What implementation" comments under the questions, you do so with the side effect of making asking questions that don't fit neatly in your little pre-defined bucket impossible and then you force users to clean up the tags afterward.