Suggestion: Mirrors for all EX mode primals
I think it'd be interesting if they implemented rare items similar to Mirror of the Whorl for each of the EX mode primals that can be used to upgrade the weapons obtained in their respective hard mode primals to an item level 100 weapon.
This gives players more things to do, a reason to run the other three EX mode primals again (and perhaps hard mode to collect the weapons), and a nice chance for horizontal weapon progression for item level 100 weapons.