How are you going to say the character is the making him viable and not the variation lol.
Because KL overall has some powerfull tools by himself, F2 is 11f and is -1 on block, spin is 7 frames, every KL has that and is good enough to play exactly the same in the neutral.
The second you put a hat trap from a string the chances or success are very slim, he is at -5 minimum, you're suggested to withstand a lot of things against all odds, so you can't just simply put your trap anyway you desire, you have to be carefully plan the best moment to get your hat out, because the opponent can destroy you with a single poke to make it disappear, even after you call it back.
Hat Trick loses all his hat related tools with the hat out, this includes the overhead starter, the spin, the tele 2, the disjointed hitbox, and so on.
Hat Calls are incredibly flawed, there is only one reliable trap which is forward trap, but is also situational because the only time you will use the trap is when the opponent is down, which allows you to slip the hat behind him since with the opponent standing you're doing it at your own risk.
Above hat trap places the hat exactly above KL head, doesn't do anything, doesn't prevent jump ins, doesn't prevent mixups, nothing above hat trap is just there
Away hat trap is a gimmick, could work if he could could re connect strings while the hat is traveling back to his head, which would pratically fix the issue of being a sitting duck when hatless but no.
Besides the worst of it all, is that hitting someone with a raw HCB is still a issue, any trained player on HT on daily basis, will always poke out crouching, this minimizes the risk of being full combo launched by raw HCB, because:
a) The hat will whiff on neutral crouch or crouch block on some characters
b) The hat will hit you out of the poke, but you're crouching, so gravity juggle is greatly reduced which KL cannot capitalized on it
c) Best case scenario, you hit him out before the hat hits you, and you get to apply pressure afterwards.