D&D 4E Spell concept to replicate 4e Bladesingers

[DEFCON 1]

I don't think it's a big deal, since the one effect of Polearm Master (a free OA at 1d10+Str damage) is so much more powerful than any of the riders on the Elemental Arc.
But since it's something that's mostly free to the classes that like it best (EKs, Valor Bards) and it's comparable to one of the best feats in the game, I'd probably nerf it slightly. Maybe make it no damage, but strengthen the rider effects.

All good points. And therein lies the design paradigm... creating rider effects that are useful, but not as useful as the rider effects granted by other cantrips that are straight spells. Which also brings up the interesting question, which is how Elemental Arc falls compared to the other cantrips spells and their rider effects? Plus doesn't the EK get an ability at I think 7th level which is Weapon attack as Action plus cantrip as Bonus action (or the other way around, cantrip as Action, weapon attack as Bonus)? So in each of these cases, the damage and riders to Elemental Arc have to be weaker than their straight comparative cousins to make up for the additional weapon damage (in the case of other cantrips) and getting it at 1st level rather than 7th (in the case of the EK ability.)

It's a lot to think about.