>>42898518legendary fights should stay completely normal, save for maybe a stat boost or two or three on the weaker legendaries. they should instead increase the HP to x6, and have it so that the legendary pokemon must recharge if you manage to take out 1/6 of the hp. essentially, a battle but against 6 of the same legendary pokemon. toxic would have to be nerfed into the ground for these fights, like maybe it cures itself of status after every 1/6 of its max hp taken down.
you wouldn't be able to catch it in battle, you would have to defeat it. then you get to play a catching minigame. this makes legendary battles more like the boss battles they needed to be, and still maintains the catching mechanic.