You can always make requests, but you cannot expect them to be fulfilled. Going by experience, the following kind of requests have a chance to be fulfilled:
Anything involving wording, e.g., the how to ask blurb, community definition, custom post notices, etc.
Rendering plugins, e.g., for equations, Youtube videos, chess games, etc.
Filters for content in posts and pop-ups (forbidden words, blacklisted tags, etc.).
In fact, we have site-specific changes of the first and third kind. Also note that some things (
help/on-topic, part of the tour, off-topic close reasons) can be changed by moderators.
The key here is the difficulty of implementation. The above things hardly touch the Stack Exchange Engine (or use existing mechanisms). You may be lucky if your suggestion is easy to implement and beneficial to many sites, but then you best suggest it on Meta SE.
While I don’t know what exactly you have in mind, any change to the tagging mechanism are far from the cost–benefit ratio that make them likely to be implemented.