Yes, indeed, it would be sort of a dictionary, albeit a very brief one --a cheatsheet, if you will--, containing only the core terms for the message group, so that it would fit into 2 or 3 lines of text. Then it could be embedded the same way the qqq files are right now. The idea is for it to work quite similarly to the current scheme of /qqq subpages. The pattern to look for would be slightly different, but the rest of the current implementation could be reused (I suppose). Or are there other obstacles I'm overlooking?
(As for your statement "it should only be product based if so indicated explicitely", yes, that would make sense if we were talking about a large dictionary, but the idea here is about very short lists of terms used by that specific product, and therefore tailored to it, which would make them not exactly reusable.)
A few remarks: "quick and small hacks" tend to turn into unworkable long term solutions. manually implementing this in qqq is not the way to go. There needs to be some process that will match words in the source message to defined terminology and translations so that everything works automagically.
I agree with the quick hacks thing, but I wasn't suggesting to manually(?) append these cheatsheets to the qqq messages, but rather to replicate that mechanism, with some changes in the pattern it uses to fetch the pages to transclude. This in principle addresses your concern about quick hacks -- unless the qqq thing is itself considered a quick hack. But if so, even though one wrong (is it?) does not justify another, I gotta say, while what you're talking about makes perfect sense and would be awesome, it seems like something that would take a while to be implemented (if ever). And on the meantime, maintaining consistency across translations stays a cumbersome task...