That said, I'm wondering why there aren't any effort put in unifying and consolidating all aikido styles. Or are there ?
There is not that I know of, but there are a lot of organizations which have friendship seminars, get togethers, and cross-training between styles and organizations.
Personally, I enjoy the differences, having trained with folks from Yoshinkan, Yoseikan, Aikikai, Iwama, Daito ryu, and independents. I wouldn't wish any of them to change. In fact, I'm a little jealous that you have access to Yoseikan Budo. Those guys do a lot of different stuff very well.
As for ranking...if I were to switch styles, I would expect my new dojo mates and instructor to hold me to the same standards they hold themselves. Unless and until I could perform their basics and any other required material, I would not expect them to look at my rank as an indicator of skill in their dojo. My rank reflects my relationship with my current teacher and dojo (and some amount of skill with their curriculum). New dojo, new instructor, new curriculum, new relationship, new rank