Currently doing a few playthroughs of Seiken Densetsu 3 / Trials of Mana. Would love to see something remedied with a hack. I'm not at the point of writing ASM or I would do it myself.
Getting the ??? seeds or the Weapon / Armor seeds is cool, but using them in the pots at the inn to produce the items you need is a huge chore. If it was as simple as saving, using the items, and resetting if you didn't get what you want that would be fine. But the RNG is tied to a battle counter so you have to leave the town, fight some battles, come back, save, then restart, load your file, and only then will you get a different result. If you don't like that one, rinse and repeat. It causes something that should take a short time to take forever.
My idea would be to write a small bit of ASM to tie the results to a RNG that isn't reliant on any counters. Would take the only real nuisance out of the game.