Well, I won't have to deal with corrosive DOT fluid for a start. Then I reckon that maybe mineral oil won't have to be de gassed and also that it may have better lubricating properties, thus reducing sticky pistons.
Really though it's just an idea I am toying with.
seals are specified for certain materials. I'm a bit baffled by your thinking that they won't degrade if not been used with dot fluid. If they say don't use mineral oil then the seals will probably swell if you use mineral oil. New or otherwise.
I am aware of the consequence of using DOT fluid on seals designed for mineral oil, however since mineral oil is less aggressive than DOT fluid I am asking if it shall work the other way round.
Just use some proper dot 4 (if that what they take) as it's the cheapest fluid to use anyway.
PS why are you flushing with water? Just flush with fresh brake fluid.
To flush out the dot fluid before putting in mineral oil, I haven't done anything yet, nor do I plan to, likesay I am just toying with the idea.