I think we would almost be regressing by setting up Big Mom as the big baddie of an arc, especially when we are going to enter the final saga after Wano.
There just isn't enough you can give for Big Mom to be this obstacle to the Strawhats post Wano. Kaido has all the conflict going for him right now with Wano's problems, its residents' connection to the SH's, Yamato being chained down, unethical use of smiles, weapons production and whatnot.
The things which make Big Mom an antagonistic force have more or less been addressed in WCI and are honestly not even close to setting her up as a dedicated villain for a future arc. If anything, her inherent childlike nature and her dream to unite all the races points towards her helping Luffy's cause by the end more than anything.
The fight itself wouldn't matter when Big Mom doesn't even have the legs to stand on as a villain post Wano despite all the potential it holds (in terms of choreography, intensity etc.) for you.