You can use cache clearing right now - there are other strategies made specially for such cases.
Also in vBET 3.3.0 cache is changed - there is separate table for each language, so indexes will be 52 times smaller and deletion will be much faster.
We are not able to tell does it will be fast enough on your forum to use normal deletion - it depends on how many rows you will have in tables. MySQL rebuilds indexes when data are deleted. And this is the reason of taking time - vBET can only provide you other ways to delete data (and it provides strategies for this). The rest is in MySQL hands.
Please just check it and if there still will be issue then it means that MySQL will not be able to handle removing 1/15 of your cached translation in normal way. In such case just check other strategies.
We can consider to add additional strategy if it will be necessary - fast deletion without rebuild of indexes. Right now 2 strategies are using fast deletion and after that rebuild indexes - this is of course the most time consuming part. We can add strategy where will be made fast deletion without index rebuild - this will made your indexes grow, so rebuild will be necessary from time to time, but you will be able to do it manually in best time for your server (some conservation time).
There is no other way we can do (it means we do not see other solutions right now

) - as I wrote it is MySQL which made clearing.