Thanks so much Sun King I haven't been participating in Theorymons for long but you have been a key figure in these discussions and thank you for looking at suggestions when I came up with them!
Onto the slate:
+ Magma Storm (it replaces Overheat so that not all Rotom forms receive Magma Storm)
This one is my least favorite because on paper I don't see getting Magma Storm as a big enough niche to change anything about the mon. I don't know what it'd do after the trap because anything it could trap and volt switch realistically out of is either going to die to a fire type move anyway or just straight up ohko it. There aren't many mons it can trap and then stay in on either. It's good against stall I guess.
+ Trace
This one is my favorite and actually quite genius. This is what I'm talking about for a theorymon. Destroys weather sweepers, destroys heatran, destroys m-sableye, destroys azu if it doesn't switch into play rough, beats zard-x before dd and gets tough claws, can check unaware clefable in a pinch after calm minds have gotten out of control, can make use of lopunny's ability after it dispatches it, when torn-t or amoongus inevitably switch in with it you can switch out and recover any chip damage you took, it can check and steal contrary from Serperior which will give it defenses each time it close combats (which actually calcs perfectly as Leaf Storm + Hidden Power Fire fails to 2HKO if you Close Combat and get the SpDef boost), bops megacham, fucks scolipede, has a neat time against non-scarf togekiss because it can get more crit hax from leaf blade and stone edge, if you lock victini into bolt strike you have a more accurate stone edge to work with, it can run certain moves to fuck with counters (taunt to beat thundurus, giga impact to beat malt and mgard), and the list can just go on and on. Probably gets the vote on awesomeness alone.
+ Shift Gear
This one is pretty good, lucario much prefers a speed boost than attack and getting the +1 attack is all he needs in many cases to start sweeping. Like just looking at the S ranks if Lucario sets up the Shift Gear it outspeeds and OHKO's both Zard-X and Megagross which is pretty huge. Same with Azu, MDiancie (on the outspeed part, already ohko'd but now guarantees OHKO with close combat so you don't have to risk iron tail accuracy), Excadrill (again outspeeds in sand), Chomp (although not tank chomp), Keldeo, Torn-T, MLop (outspeeds), Latis, Manaphy, pretty much everything that had good matchups before are donezo. Its best switchins are all 2hko'd by the wrong move (MSableye, Lando-T, Skarm) so they have to be careful about switching. It is still hard countered by MSlowbro and Slowbro but you can run Crunch over Extremespeed if you want to take care of regular bro. Honestly it's close to as OP as Geomancy Sylveon would've been and that's the only reason why I don't want to give it a vote only things keeping it from being that OP are the fact that it can't set up on as many things due to its fraility, it isn't +2 atk, it doesn't get a defensive boost, and it has life orb recoil. It does have two legs up over Sylveon in that its coverage is better and it gets Extremespeed to keep from getting revenge killed which is pretty huge so it puts it pretty square to that level of power. I just don't like how easy this thing would win the game for you. It's almost exactly like its mega except a little less power and more speed (and its physical only).
+ Fairy (replaces Normal typing)
This is good if not really obvious. Having actual resists on top of its enormous health and spdef may just give it the niche over chansey its been waiting for. It gives it the ability to front many of the physical attackers and attacks that would otherwise laugh at it like Weavile, MLop, and Keldeo and can then return fire with dazzling gleam. Having dragon immunity means it can get a predicted switch onto Dragonite or Zard-X and get a Twave off now if they aren't +2. Also it counters the shit out of Torn-T. On the other hand, Blissey has made her life worse against Gengar and Heatran. Also I feel as if it probably gains more poor matchups to physical attackers than it lost. Exadrill, Bisharp, Megagross, Scizor, and Scolipede all got better matchups. Conkeldurr doesn't mind it that much due to Poison Jab. I think it actually might be a tad overrated this switch, it still has many of the same problems due to its defense but giving it some better matchups that even Chansey envies may be enough.