Ou it wouldn't be that hard. Equip Black Map and go to the Looper Nest. By the end of the game you should start with 12sp so you cN use Aika's move that she learns after Lambda Burst, or stick with that if you don't have enough. It should kill most of the Loopers except the stronger colours and maybe red. But eventually you'll start with 14 and Rain of Swords will end it in one hit
It would just be an utterly annoying and pointless grind
Damn, forgot about Rain of Swords!
But at end game (of first run, I suppose) I started with 13 SP
Vyse LV52
Aika LV51
Fina LV50
Enrique LV48
Aika LV51
Fina LV50
Enrique LV48
So I never had enough to start with Rain of Swords, and I don't remember but maybe some of the loopers like Blue and Purple moved too fast and would just flee anyway. Fleeing is not something to worry about I guess, probably don't get much EXP from loopers anyway.
Was it just me or did magic attacks do little damage to loopers too, because I remember frequently using Lambda Burst on Green loopers and inflicting 0 or 1 points of damage sometimes. Never tried with Omega Psyclone though...