How is Shiryu a bum? He was Magellan's equal pre timeskip, the same Magellan who had Jimbei, Ivankov, Crocodile all choose to run away rather than face him even combined. Same man who low-mid diffed Ivankov.
That places pre timeskip Shiryu around the level of the OG Yonkou right hands (minus Beckman since we know very little). This means that base Shiryu is already King lvl, with his gimmicks he can be pushing into another territory entirely. Granted his invisibility looked like dogshit on Hachinosu, and invisibility does seem underwhelming af, but I think Oda will give him a broken gimmick as always. Either an awakened invisibility fruit or another df in the mix for his weapon or something.
Edit: I wouldn't even be surprised if Shiryu has or gains a supreme graded blade, at the very least I expect his blade to be great grade class. I'm just hoping he doesn't get some clown ass zoan fruit for his blade and turn this into another clown fight for Zoro. Something like a great grade blade with diamond fruit for added offense and defense would be based, don't know how it would be possible but you never know.