I don't like it. Lots of sub-boards can bring worry. If you want to talk about something specific for a Bitcoin wallet, use a Wallet software sub-board. If you want to ask questions related to wallet software, use that board. If you're interested in improving your competence around security, you should visit the proposed board.
We should also have a separate privacy-related sub-board, in my opinion, but that's off-topic.
Potentially having a privacy section that's a child of security as they're somewhat related or simply a dedicated Security & Privacy section. Probably one of the few times I'd like to see something implemented not based on demand, but because I think it's somewhat important to understand. Plus, I could probably talk security a lot, and would have some threads in mind to contribute to the section which don't really fit anywhere worthwhile currently. Off topic or very loosely Beginners & Help maybe.