First things first, I love the idea of this team, DS Uxie with Memento is pretty cool and going into a sweeper for some early damage is nice. However there are some nitpicks.
First, you should be running Swords Dance Gallade over Feraligatr. Gallade is a monster in UU and with the DS up and Memento on a pokemon, Gallade will be able to rip through teams with a free Swords Dance. The only problems are Gallade's counters, which are taken care of by Registeel anyway. The set should look something like:
Gallade @ Lum Berry
Steadfast
Adamant
6 Hp/ 252 Atk/ 252 Spe
~Swords Dance
~Close Combat
~Night Slash
~Shadow Sneak
CC and Night Slash provide ridiculous coverage for your team while Shadow Sneak is for priority.
I would also like to see Blaziken changed to Honchkrow, another amazing UU pokemon. Honchkrow has amazing coverage and can go with a mixed set with Heat Wave to hit steels. Your opponent can try to predict what move you will use out of Honchkrow's huge movepool but either way, Honchkrow's natural bulk and huge movepool make it a huge threat under dual screens. I would go with the following set.
Honchkrow @ Life Orb
Super Luck
Naive/Hasty
224 Atk/ 48 SpA/ 236 Spe
~Brave Bird/Drill Peck
~Sucker Punch
~Substitute
~Heat Wave/Super Power
Send in Honchkrow and setting up a Sub on the switch will let him wreck havoc with your opponent. With a sub up, Sucker Punch becomes amazing since your opponent can't do anything besides set up to avoid it when you hide behind a Sub, Brave Bird is powerful STAB while Drill Peck conserves his HP. Heat Wave hits from the Special Side while Super Power adds a strong physical move. If you go with Super Power, max out Atk and Spe. If you want a more specially based attacker, you can play around with the EV's, but this set should work out fine since Honckrow's main counters are faster pokemon, but a Sub behind DS for Honchkrow means that something is going to die.
Also, I really don't like Kumar's idea of Rapid Spin on Technitop. Technitop is more of a revenge killer and sweeper and Fake Out really does help with the extra damage. There's also no real need for it at all since you have 3 pokemon vulnerable to Toxic Spikes, and all of them are sweepers, so they won't enjoy the Toxic damage, but on the other hand, it does not hamper their core purpose and prevents random other status like Paralyze and Burns stopping your sweepers. Also I see Hitmontop filling a really necessary role of revenge killing and using him to spin defeats that purpose. Hitmontop seems like the poke that can come in and clean up the guys weakened by your sweepers. Which he fills really nicely with Fake Out to gurantee OHKO's. Since most of your team defeates Mismagius anyway after a boost or by walling with Encore, I don't see the need for Bullet Punch at all. In fact, Close Combat would work much better. Close Combat is ridiculously powerful and helps Hitmontop overcome Registeels that try to come in and stop him.
A third nitpick would be Thunder Wave over Toxic on Registeel. With two ridiculous walls, you could easily spread the para so your sweepers could come back in after the DS goes down and outspeed stuff.
Anyway, I'm definitely going to try out DS Memento Uxie now with my UU team because it looks like it can cause a devastating sweep from something. I hope my rate helps.