Probably it just so happened that he felt nobody submit anything that fit for those classes.
I mean, I can't really think of a good alternative for them either (I mean, it's going to be really hard to give Summoners any more/different gimmicks than they already have), and it's gotten pretty difficult to contact Mamare now. Probably better just to let it drop.
I feel Paladin should have been Guardian instead of Pirate.
It makes more sense to me.
I have studied history of war.
Especially since that nation was famous for it sanctioned pirates called Privateers.
Summoner doesn't have many if any alternative names.
I been searching and come up with zero.
Pirate/Samurai rely more on parrying and countering, though, rather than straight-up tanking. Knights can parry and counter, but I feel like in terms of armor, they fit more to the Guardian role. Not to mention that the Paladins were knights (according to legend).