Considering that Broly definitely seems to at least have stacked his human Oozaru Rage form onto SSJ in his Full Power (LSSJ) state judging by the pupils that returned as he was about to be hit by Gogeta's blast, is it possible that his SSJ Full Power form is tapping into his full potential...
I think he needed time to think of something to one up Pegasus in scale. Pegasus was already the fucking creator of the damn game, so he had to flesh out the concept of God Cards and the holder of the final two Millennium Items (Necklace and Rod) before he could continue to go on with another...
Berserk and Vagabond are both discontinued and I don't read Vinland Saga anymore (probably won't until it finishes) so... could go either way. I'll choose the former though just to see the HxH and Narutofags seethe.
Wouldn't Cell have better stamina than Gohan though since Gohan only recently attained SSJ2 and Cell seemed to have MSSJ level stamina without ever training