It would be nice to have tags for threads.
That is a nice way to qualify content, give it more context and such - other than the subforum/category it is in. Helps with search too and are a good way to prepare or replace forum splits. So you could slowly introduce tags, at some point in time retag old threads and at some point in time move them all at once - or not move them. It has many benefits, as long as the tagging is applied, the amount of work stays the same to move to a different category, but in the case of tags the energy put in is conserved.
A related, but somewhat different, approach can be seen in the VoIP forum on DSLReports. There, all VoIP discussions are in one forum. However, a thread can have a "Group" assigned to it.
I know group tags from a different forum, they even lead to not index them in the search, so their content does not end up in the search results. This might sound harsh, but either content is important enough for a "question -> answer(s)" form and deserves its own thread/blog/faq/wiki article or it is "discuss!" kind of content. Under the assumption that people search for answers, the discussion might not be that valuable - forum internal search that is, google still finds it all, listing posts of users still works.
Another real problem was people answering by referring to use the search function (no results, no links). This means search results contain keywords (in the question) and the only answer is a reference to the search function. This is short of trolling - on a big scale - it might not be ill intended, but becomes a problem. Next to it not being helpful at all.
Using real tags would have the additional benefit of being able to classify a thread with more than one.
It gives it additional context, allows filtering the view - in case you are a viewer and just want to look which topics there are or are overwhelmed by the variety. The worst thing that can happen is missing tags or wrong tags, but that is the same risk as with topic titles anyway.
I used to spend some time automatically qualifying ten+ years of threads (i think several 10k), meaning to automatically tag and sort them based on some regex-based threshold method (checking the first post only), but still needed to look over and hand sort and then automatically move them. I mean once exported to csv/excel that goes quick and it worked well, but that took a database with qualifiers in them (that in itself was crowd sourced and later curated, spiced up with external data). It was needed because category splits happened after several years of existence, but moving was too much hassle back then (the mod interface was slow and deep - per thread). So having a well fed database of qualifiers (here: test equipment) enables this kind of use.