Good concept, but needs works. Since you asked for feedback:

Biggest issue is that whipping and spanking leave very different types of marks, and you'd be better off with multiple loras.

Whipping, caning, etc leave long strips, which can be layered (or not). Typically has a sharp change from marked to unmarked areas.

Typical spanking, paddling, etc leave more rounded marks, and there's a more gradual reddening. There are specific types of paddles can produce the more dramatic marks when used repeatedly (and with accuracy), but those are the exception rather than the rule.

Currently, you've got mark shape that resembles spanking, and mark sharpness that's more appropriate for caning.

Another issue is that it sometimes overdoes the welts and they look like growths. Not really sure how to resolve that.

Another issue is that this adds whips. Many (most?) people who are going to use a lora like this will care that the marks don't match the tool.

Nitpick: It's limited to butts. Yes, that's the most traditional place to spank, whip, etc, but this is AI art. Expect people to try to use this everywhere. There definitely are images out there of abusing any/every part of the body that you could use for training if desired, or you can keep it limited to butts.