This is probably already being said but I don't have time to go though all 54 pages right now.
But here are my thoughts and Speculations on Mega Sceptile (one of the most exciting Megas to me) in terms of its battle potential…
non-mega Sceptile isn’t a “bad” Pokémon but its biggest issues in the past have been: 1) Lacking good coverage with its STAB Attacks (or powerful coverage in general) And 2) Having better sp.atk than atk while also having a movepool that leans really really physically.
Like, the move Leaf Blade was originally made just for Sceptile. But back then all plant attacks were special, it wasn’t until 4th gen that moves could be special or physical independent of typing (one of the few things 4th gen did right) But it kind of sucked for Sceptile who has a nice sp.atk but very average atk. It is basically left with a ton of good Physical moves and boosting moves like Swords Dance but is limited to Leaf Storm and Focus Blast as its only good special moves. It also has Dragon Pulse but there was no reason to use that before it could get STAB on it.
Anyway even before going Mega, Sceptile has really impressive Speed (base 120). Its ability to revenge kill and possibly sweep is pretty much already going to be solid even if Mega Sceptile has even unimproved speed. So were will most of the extra 100 base stats get placed? My guess is a minor amount in speed and its defenses and a lot in sp.atk. Mostly because a little bit of a defense upgrade with a heavy upgrade in one offensive stat has been the trend in most offensively oriented megas so far, and also because the ability Lighting Rod (which grants sp.atk boosts) hints that they intend for Sceptile to remain a Special attacker in its Mega form.
If I’m wrong and Sceptile gets an upgrade in Atk or just gets equal upgrades in both its offensive stats then Mega Sceptile will have it made as a viable Mega option. As it can use Swords Dance and it’s great physical movepool to become a dangerous Sweeper or even use a mixed attacking set that switches into Electric attacks, fires off really powerful Leaf Storms but then uses physical moves for its other attacks so it doesn’t have to witch out after the Sp.atk drop. (Like “haha stupid Hetran thought it could switch into my Leaf Strom but now I’m hitting it with Earthquake!”)
However if my guess on stat upgrading is right and mega Sceptile doesn’t receive much or any physical atk increase then Mega Sceptiles success is going to be largely dependent on an expansion of its movepool to include a few more Special attacking options. As, outside of Lighting Rod, which is unreliable, it has no way to boost its Sp.atk, it can’t perform that well as a sweeper. And while STAB Dragon Pulse will really help with Sceptile’s “coverage” and power issues it still lacks a Plant STAB without serious drawbacks (Leaf Storm forces you to switch and Giga Drain, the next best thing, is just a weak move) And Focus Blast it’s only good 3rd attack, while insuring that Steel types can’t just come in for free, is also infamously know as “Focus Miss” is risky with a 70% hit rate. (Not to mention if a Steel type switches into your Leaf Storm it’s not like Focus Blast will hit them all that hard anyway after a Sp.Atk drop.) Anyway I think you see where I’m going. Basically Mega Sceptile with no Atk upgrade needs 3 or 4 good moves that would help it out on the Special spectrum of offense, else it’s left with a number of drawbacks and a huge lack of variety that makes it really predictable.
If Mega Sceptile doesn’t get a physical attack upgrade or a more expansive Speical move pool it will likely end up like Houndoom. Powerful and cool as a Mega, but probably not worth using over another Mega if you’re aiming to win your battle. Actually it still will have more niche uses than Mega Houndoom though. Simply having high speed and attack has always been a mixture for some success in the Pokémon world even with sub-par coverage. More specifically though Mega Sceptile will be great at revenge killing enemy dragons since it can out speed all of them unboosted (except Noivern) and will totally own them with its own Dragon attacks. In fact regular Sceptile without any speed upgrade from its mega is already capable of out pacing Adamant Dragontie after a Dragon Dance. If Mega Sceptile has a big enough speed boost it could be capable of outspeeding other Dragon Dancers as well. But probably the biggest and most obvious use for Mega Sceptile will be that it is THE #1 counter to Rotom-Wash. Rotom-W success is largely attributed to the fact it can fire off Thunderbolts and Volt Switches really freely (something other electric types can’t do because of ground types) however Rotom-W gets Hydro Pump the ability Levitate which means it basically wins the match-up against any Ground type that tries to switch in on it. None of this applies to Mega Sceptile who get the same electric immunity but with a boost,x4 resist Hydro Pump, and can easily KO with STAB Plant attacks. Plus Mega Sceptile potentially won’t care that much about switching into a Will-o-Wisp. If Mega Sceptile starts to see any use at all, scared Rotom-W’s everywhere will have start running Hidden Power Ice out of the hope that they can catch Sceptile on the switch in. Even if they do this it will degrade Rotom-W’s utility a lot simply because of the “waste” of the move slot. Simply having a Mega Sceptile on your team makes everyone (but especially Rotom-W) think twice before clicking an electric attack.
