Nice article man! I'm currently running a very similar deck.
* 4 Pidgeot-EX EVO 64
* 3 M Pidgeot-EX EVO 65
* 1 Magearna-EX STS 75
* 1 Registeel AOR 51
* 2 Remoraid BKT 31
* 2 Octillery BKT 33
* 1 Professor Sycamore STS 114
* 1 Skyla BCR 134
* 2 Pidgeot Spirit Link EVO 81
* 3 Shrine of Memories PRC 139
* 1 N DEX 96
* 2 Lysandre AOR 78
* 4 Puzzle of Time BKP 109
* 1 Parallel City BKT 145
* 1 Hex Maniac AOR 75
* 2 Float Stone BKT 137
* 4 Ultra Ball FAC 113
* 3 Professor Birch's Observations PRC 134
* 2 Mega Turbo ROS 86
* 4 Max Potion BKP 103
* 1 Energy Reset FAC 98
* 4 VS Seeker PHF 109
* 1 Team Flare Grunt XY 129
* 4 Double Colorless Energy FAC 114
* 6 Metal Energy XYEnergy 7
Your ideas of pidgeot changed my deck a lot (fe the magearna, the 1/3 syca/birch and 2 spirit links) but maybe you can think about a few extra cards. What if you play against a carbink and that hex maniac is priced? So it will be hard if you don't have a non-ex attacker. Thats why I put in Registeel > cobalion and mewtwo you mentioned. Registeel is also good if playing against M mewtwo (or darkrai), which can counter this deck. This makes sense why I also run team flare grunt in this deck.
I'm not a fan of Assault vest bc you want to do a lot of dmg w your mirror move after the max potion combo so I removed them and found my space to play 4 puzzle of time.
I also feel like 1 N is more then enough. Most of the decks are running N and it will be used against you a lot but if you have your octillery running there is no need to worry.
I feel like energy reset is a must have card in this deck. This card is INSANE! This card gave me the game so many times against many kind of match ups.
I once had the combination of: draw puzzle, had max potion and vs seeker in hand. Played vs seeker for Skyla, skyla for 2nd puzzle, brought back mega turbo and energy reset from discard pile. played energy reset for everything on M pidgeot (dce and steel), then max potion, mega turbo and could attach my dce as energy of the turn and that won me the game against Volcanions (hate that deck though xD).
Pidgeots are so fun to play with and people don't even know what they do until they see your combination but then hitting 130 (or an higher mirror move) every turn isn't something that can be taken lightly.
Any changes I could make if I had to:
A) -1 ultra ball +1 parall
B) -1 N, +1 Team flare grunt
C) -1 ultra ball +1 energy reset
Feel free to comment if you have any advice on this one