Hi! Thanks for the rate!
Now, I can understand your concerns about Reuniclus, Keldeo, Lati@s and the like, but the team is capable of handling them. Sp.Def Skarmory can take most of Lati@s' attacks well, and HP Fire/Surf is easily absorbed by Rotom-W. Now, Reuniclus can be annoying, but it's true Skarmory can phaze it out, and the fact that it has to rely on Focus Blast to get neutral damage is helpful. Keldeo I suppose can put pressure on the team with Rain-Choice Specs-boosted Hydro Pumps, but that again requires it to actually hit each time, and at the very least Rotom-W/Celebi can revenge kill it. Now, you also claimed that Alakazam 6-0's the team if it has focus sash. I fail to see how this is possible. True, nothing can kill it in one shot, and it can retaliate, but you're overlooking that fact that Alakazam can be taken out by a combined effort. For example, Lucario can Extreemspeed it to break the sash, while Salamence can come in and kill it with Outrage, possibly starting a sweep. I also notice you also use the idea of "can switch to a counter" as an argument for a threat. That's assuming said counter is still alive, and it should also be mentioned that Hydreigon and Salamence have no counters, so proper prediction can remove threats from play.
Sorry about that, now about your rates...
The reason for not using a defensive Celebi has already been mentioned, so I don't think I need to mention it again. Jirachi over Hydreigon, I'm afraid, is something that we really can't do. The team is based around Hydreigon; therefore, the goal is to make a team that works best with it in it, and replacing it goes completely against this goal. I'm sorry if this sounds harsh, but Hydreigon isn't something that can be replaced on the team; change the team to suit Hydreigon, not the other way around.