I pretty much always use “View unread posts” until I’ve seen what interested me, then mark forums read. So categorization doesn’t affect my experience much at all.
I think these proposal is good, except for a few things. “Introductions and Welcomes” is worthless and should be omitted (a single thread could be added instead to do that, like we have now). Also, there should probably be a “Other Systems Development” forum, since Inform, Inform7, TADS2, TADS3, and choice-based, would not be the only ones; there are others too (such as ZIL and OASYS).
However, note that if everything is adjusted then you will have to move the old messages properly too and this might also problem, because the messages are not currently categorized in those ways!