Saw the photos on your other post. Very nice looking boat.
Dry bilges are certainly achievable, even with steel
. Had a steel
boat and the bilges, except right under the stuffing box where I had the necessary drip, where dusty. Same with my last fiberglass
boat. Can't say the same about the current
boat but, like you, I'm getting to it.
Sure oil is a rust preventative but mixed with water I think the "benefits" would be mixed at best. Not to mention oily bilges tend to develop rather a bad odor
which detracts from the live aboard experience and can lead to solo sailing.