I will answer both questions here. For the first question, you are right that the rules state that “If the character is below the maximum station for their regiment, they may roll for promotion.”
Based on the example, I do think the intent is that you can be promoted OUT of a regiment - and that feels better to me. I think if you managed to deploy with the regiment (and they survive and are not found out as a coward) then you should be eligible for promotion. (The promotion target limit for training and garrison assignments is still in effect though.)
I think it’s more important that you come to a consensus. I don’t think going from S4 to S5 matters too much unless you’ve added some win condition where you’re racing to S8. If you do let them get promoted, then they won’t lose regimental membership until the next Station Phase. Anything could happen, they might even dip back into S4.
For the second question, a trust’s size is always equal to its owner’s station. So yes, when an S1 player transfers a trust to an S3 person, it immediately becomes H3. It’s great that a high station player is paying lower station players to make trusts. I think this kind of naked corruption is what Commonwealth is all about. If this is a problem, I think the best way to deal with it would be to harass them with a militia, concoct grounds for monomachy, or use a salamander.


