I'm 7 champions away from having collected every one of the 207 champions in the game. For me, this is a very big achievement and I'm very proud of my progress over 7 years of playing this game as a F2P player, the countless sleepless weekends of arena grind and broken windows throughout my house I have had to replace because of numerous bugs plaguing my game play

I'm not too phased about collecting each one at a specific rarity, and casually settle for running arena just to drop the 3* version of a champ, especially newer champs, just to tick them off my list as "collected":

I'm on my way to complete LoL for 100% rewards to tick Ultron off my list, my question here is, what is the ultimate possibility of securing the 3 unicorns on this list?
I'm at a point where I'm dropping more maxed signature crystals than any new champs, and have, to date, opened over 317 crystals in the hopes of dropping Immortal Iron Fist, without luck? Is there anything specific I can do, to increase my chances? I really, really just want to tick him off the list.
Thanos and Weapon X is the other two unicorns and I've resigned myself to the fact that I will just not get them. Ever. As a F2P player, I do not have the financial means to drop greater gifting crystals in excess needed to potentially drop Thanos, and as Weapon X was a special gift for those worthy of being in the top running, will not see him in my roster, sadly.
Will there ever be an event or opportunity, like a special crystal sale where we could potentially drop these 2, even as 2*'s? I'd gun for a special offer like that without hesitation, again, as a collector, it's about ticking the champs off. I don't care about rarity at this stage that much.
And then, as I was working my way through the available (playable) champs in the game, something on Authm.ai struck me as odd, so I went back into the game to confirm and lo and behold, there is one champion that is not available as a 5*. Out of the 207 playable champions, there are only 206 playable 5* champions in the game.
@Kabam Miike when, if at all, is Deadpool coming to the 5* pool? That to me, would be the most ultimate drop of a champ and I'd spend 10 days without sleep to grind him in arena if I must. I want Deadpool as a 5*, please