Thanks! Sorry if it was a bit confusing a question.

The work hotel is indeed a resort property. There are non-resort properties in Bali (I believe), e.g. I've had late checkout before at the Courtyard Seminyak.

Anyway I am thinking to avoid the uncertainty of a very early check-in at the work hotel, I'd book and pay for an additional morning-sleep hotel myself, on Marriott channels.

So let's say:
I'd arrive Monday 10am
I can check in to the work hotel after 3pm Monday, no benefits expected and further, they currently look booked out for Sunday-Monday. So I think there's very little to expect there.
I am therefore thinking of booking my own hotel for the Monday 11am-3pm (i.e. with a reservation starting on Sunday). Thinking I might have a better chance of a 4pm checkout at a limited service brand (e.g. a Four Points). But I'd only be turning up ~10.30am.

Never done something like this before, but the elite night would be useful. I wasn't able to find day rates for Marriotts in Bali (which don't get elite night credit) either.