I'll just put it in simple words. I think i'm pretty much done after this, you don't seem to be understanding, so I won't bother anymore.
Nikola is used so players who disconnect or accidentally faint a legendary Pokemon during the battle can have a second chance at catching it. That is how Nikola is supposed to be used, it is not used for anything else.
Adding Keldeo and the Kami trio to that list just so you can battle them and have a second chance at catching them doesn't make any sense because those legendary Pokemon already respawn at their respective areas if you happen to fail at catching them.
You're using Nikola as a free reroll, which is not what the boss is for. That's it, it's not that hard to understand. Either i'm oblivious or you are.