andwhyisit said:
The powers of the crown come from Ballos, and due to the link between red flowers and the crown
It's uncertain whether such a link exists. The only thing in the game pointing to it is that the Doctor is capable of controlling frenzied Mimigas, which could well be simply because of the Crown being powerful.
Kazuma talks about a link with the Core, but the Core and the Demon Crown are totally separate.
it is likely that the powers of the red flowers stem (get it) from Ballos as well.
Not particularly likely.
Since Ballos is only able to drag the island to the ground upon the Core's destruction it is likely that the Core restricts his use of magic.
This is likely.
Once the Core was destroyed Ballos was likely no longer bound by the crown
Ballos wasn't ever bound by the Crown. Misery was the one cursed by the Crown. Ballos created it, his soul infuses it, and in a reversal of the One Ring situation, he's still the part with all the power.
or much else for that matter, rendering the crown, flowers and crystal useless (in theory).
The Crown is indeed rendered useless by Ballos's death. The flowers and crystal may have been rendered useless by the Core's destruction, but Kazuma's probably less reliable than the Doctor as a source of information.
In either ending there would be no more crown bearers or red flowers since Ballos would either be free (normal ending) or dead (sacred grounds ending).
Ballos was trying to commit suicide by smashing the island into the ground in Sue's ending as well, so yes, he would be dead either way.
But him being free would have nothing to do with depowering the Demon Crown. It's Misery that's bound to the Crown.