Should they get a Spartiates brigade!!!

You mean their uber hoplites with 5 (max) morale isn't enough?

If place the scared band unit with a five-star general and any of the spartan hoplite unit with five-star general the scared band unit would crush the spartan hoplite unit every-time.

yes but in that case the sacred band unit is un-trainable and the Spartan hoplite unit can be trained in all their starting territory plus Sparta is past their Glorious says so to speak after the Thebans defeated them at Leuctra Sparta was never really able to recover

Yes but its a game and should have option having elite units in any sandbox including the spartan spartiates brigade unit.

Thats a pretty remarkable claim. If you want to be overpowered and unbalance the game, you can use the console to do so.