Tough matter imo
There are certain limitating factors:
- Rokushiki + stats: Hybrid WhosWho and Vergo
- Stats in general: Dukes, top scabbards in general, Jinbei, M3, Doffy etc.
- Speed + CoO spec: Sanji pretty much, who also happens to be one the best/most skilled martial artists
Those are tough nuts to crack.
Best case scenario:
He's specialized in speed base techs (Soru/Geppou), which go well in hand with his seemingly great CoO spec, while he uses something like internal destruction haki as his main attack quirk (Episode of Luffy).
Basically being less durable and physically weaker than guys like Vergo and Drake, but much more agile, maybe faster, while he compensates lacking strength/AP with internal destro haki, making him a low high tier overall..?
Basically: A weaker, but faster/more mobile base Sabo at best, but I dunno..