Ragnarök Tyr
Warrior
To begin, I care little for the, "Too many Batman characters" line, take it somewhere else. Personally, I've believed Scarecrow could be a potential Fighting Game character once he debuted in the original Arkham Asylum game. His appearance & design in Arkham Knight cemented that belief. Some may say that Skill-set wise, Scarecrow has never really been depicted as a master of martial arts outside of some renditions such as his Noose-Around-The-Neck appearance in the "New Batman Animated' Series. Or his Scythe wielding version in Batman: The Brave & The Bold.
Generally, outside of his Fear Toxin he's depicted as being relatively harmless when it comes to physical combat. Of course that all goes out the window in Fighting Games where characters that would normally stand no chance are given equal footing (in the idea of the game)
As far as possible play style I've always imagined him having something of an MK9 Freddy set. Long range claw attacks with maybe a DOT effect such as F.A.N.G or Venomous D'Vorah. His trait with the Fear Toxin could have one of multiple effects (reversing inputs, slowing meter gain, slowing character etc) Almost like Valentine in Skullgirls who gets access to multiple effects based on whatever poison she loads into the syringe.
There are infinite possibilities with the character and regardless of Tier he would be my official Day 1 Main. Of course if he's terrible, i'll have a Top Tier backup. But he'd be my central focus.
@CrazyFingers (If Swamp Thing doesn't make it)
and GunShow who may not be on this site anymore, may also join the cause.