>>35230247I'd change the catching mechanics to rely less on RNG and more on skill and strategy. When you use a pokeball you'd have to time a button press on a reticule whose size is dependent on the pokemon's HP, catch rate, etc.
I'd also add some "boss fight" mechanics to legendary battles, so that they have sort of a "shield" bar over their HP bar that you have to deplete before you can actually damage them or inflict status or capture them. The shield regenerates periodically to compensate for the no (random) chance of failure when you do try to catch them.