I'm in favour of not capping it either. It doesn't seem as though it would have a big result on rewards and could be detrimental overall to their aims. If you only have five teams available players will be de-incentivised to work on other toons that are permitted but are outside their top five teams. I know I've already dropped some extra gear on my jawas, and they're the sixth team for me. If it was capped at, say, ten attempts per raid (to prevent players doing lots of undermanned teams as if that would make a difference) that's enough to allow players to try out new things and keep working on a (slightly) broader roster.
Maybe their intention in all of this was to prevent one or two big accounts in small guilds from submitting 7/8 attempts each and enabling a host of smaller accounts to get the first few boxes in Krayt. If so that seems a bit silly IMO.