On older chronicles like c4/interlude substack server can be easly ballanced with just a few skill changes, on HB little more changes are required but it is still doable. When it comes to H5 where every single class is strong on its own, can do hell lot of things and is way more powerfull than it was on older chronicles (just compare tanks on interlude and on h5) , balancing a h5 stacksub server is huge challenge. I played on h5 stacksub some time ago and it was done kinda nice. No idea how admins gonna ballance things on this server since there are no informations at all, but there is a lot of work to do.
Removing cert skills is a obvious thing.
Kamaels are part of this game (like it or not), however allowing them to take stacking sub or completly removing them is not a good idea.
IMO keep them in the game but dont let them take stacksub.
They are strong on its own and can fit every single kind of party, trickster in archers, berk in close-range one, slh in mage for example. They will be still a viable choice even without stacksubs.
One more thing about rates. I think that brand NEW x10 stacksub server, without history of previous 1+1 projects have a good chance to succed, just because "lower-rates" server require a solid online numbers to create stable economy and "available pvps" to keep ppl playing. I doubt you will be able to gather such amount of players, tho i hope you do.
Anyway, you should consider boosting rates to something like x20-x25 or maybe more (mid rate server?).