There's already a review on Chrono Trigger Platinum.
I may play through it but I loved the implementation done by the 'Chrono Trigger Level Zero' patch. Now THAT is a nice challenge without being too brutal.
For your FF3 hack, I don't really see the point of increasing item costs or making it more grindy to gain XP/Gold. The real challenge and joy of playing a game (for me) tends to come from engaging and interesting boss & miniboss enemy encounters. You plough through the trash mobs to get to the main event and the anticipation of 'holy shit this is for realz' makes it that much more exciting. When I redid Shining in the Darkness enemy balance for my Thornwood Terrors patch, I kept this aspect in mind and it makes a WORLD of difference.
I haven't played the FF7 one you made.
The problem I see with all 3 of your hacks is that they aren't compatible with the existing retranslation patches that are already released. When a patch isn't cross-compatible with a retranslation patch then that makes it far less likely for me to play it.