What would you do to give Beheeyem a bit of a boost? Do you think widening its movepool to give it a niche that’s not already filled by Reuniclus is possible, or is an evo (mega or otherwise) the only way to save them from the metaphorical Tartarus that is forgetabiity?

Let’s see… at the moment, what Beheeyem is good at is slow, powerful special attacks, often within a Trick Room, which Beheeyem himself can set up.  Which is fine, and Beheeyem’s not even bad at that, really; if he can get a power bonus from Analytic, stacked on top of an item boost, his attacks seriously sting.  It’s just that Reuniclus, as you note, is significantly better at exactly the same things, being tougher, and protected by either Magic Guard or Regenerator, which makes spamming Calm Mind a solid option.  And to be honest, I don’t really think movepool stuff really changes that.  You could add Focus Blast, I guess, but that’s just copying Reuniclus more; Dazzling Gleam or Flash Cannon might be justifiable, but I’m not convinced they would help much.  Zap Cannon would be hilarious, but of questionable value.  Beheeyem’s support movepool already has just about everything you could ask for, except maybe Hypnosis (…come to think of it, why doesn’t Beheeyem get Hypnosis?).  The trouble is, being as slow as Beheeyem just doesn’t work for a Pokémon that physically frail.  I think at minimum you have to rejigger his stats… swap his special attack and physical defence, maybe?  Dunno if that makes him better; I mean, it helps on the “different from Reuniclus” front, I guess, but those souped-up Analytic special attacks are most of what he’s got going for him at the moment.  To make matters worse, Beheeyem’s base stat total is at an awkward spot where getting another evolution seems really unlikely… I don’t know.  Mega Evolution might be the only way to go with this one.