I'd say that an option could be that you still have the stages of ingestion as before, only that each initiated grapple/vore check allowed you to do three vore checks, and if all succeeded, the victim was instantly swallowed, if two succeeded, the victim was ingested, and if only one succeeded out of 3, they were only grappled. That way the feats that allow you to consume your opponents with less checks would still be useful, by making your vore-checks more consistent.