@ashishbhatia, after some investigating, it looks like this is not something that can be easily solved with an out-of-the-box solution. You might be able to build a wrapper API handler that only supports OAUTH, but that would be a bit of a long, hard road to travel for a workaround.
I suggest you explain your usecase and submit your idea for this feature to https://ideas.sailpoint.com/. The team takes customer and partner feedback very seriously & you might be able to get this on the roadmap.
Best of luck to you. We hope to see more of you in the Developer Community!