Lately I've been feeling the same, too. I've been a little, and a sub in general for most of my life, and as of late I've been real curious in attempting the other side of the whole kinky spectrum. While I have very little experience of 'actually' being a mommy, and I don't see it being a massive side of me, I do see myself taking care of the right person if the time came up. Who knows. Maybe the 'heart of the mommy' was always inside of me, and I just never realized it until now.
That being said, I'm fairly certain a role switching dynamic could work out, as long as you are positive both parties are happy fulfilling both roles. I know two friends of mine who are both Doms who will go out of their way to sub for each other, and they are a pretty inseparable couple.