Personally, I've been stuck at lord for ages. Been doing empire missions with every empire faction I can find for a very long time (I think I got to lord around 1.1). I was under the impression that it is just a RNG system as to when the mission appears. No matter where I've gone, who I've talked to, or what my rep is, the mission for Baron wasn't showing up anywhere. Then when 1.3 Beta launched, I installed it and started playing. Lo and behold! The first time I open up the BB in power play there it is, my naval ascension mission for baron. In the beta server, under the new mission system.
Now, back to the stable release server. Still no ascension mission for my imperial rank. Rep is pretty much maxed with every imperial faction I've found. I see no reason why this mission won't pop up for me. After seeing it pop up immediately in beta but not once in stable build is leading me to believe it IS currently bugged a bit.
I get that random number generators are RANDOM, but I've been looking for this mission for so long, I'm doubting it's just a problem with the RNG not drawing the numbers I need. The more likely problem IMHO is that the current system isn't working correctly.
Just my 2c/observations...