For the 3rd major update I have sought to rectify a notable absence in Solar Nations, that of individual leaders. However, most Grand Strategy games, at least in my opinion, do leaders in such a way that they either don't resonate with, or actively undermine other systems. As such, the leader system in Solar Nations is very different from what you're used to, but is also specially designed to be interesting while also being easy to understand.
Characters in Solar Nations are represented as a collection of 4 stats, gained by acquiring more traits through levelling up or personality skills. These stats are used to execute missions which cost a certain amount of the characters' health.
There are a wide variety of missions to choose from, ranging from simple investments to forced vassalization of an enemy. Characters are able to gain experience through these missions, which have a number of special powers that could be extremely impactful if well used.
For example: this operation immediately replenishes the morale of your units. It can be used during battles as well, provided the battle is close enough to a region your leader is stationed in.
Your leaders are also not restricted to your borders. You can send leaders into enemy or neutral territory with less than friendly intentions, and there are many operations you can use to wreak havoc on an unsuspecting enemy.
However, you are not defenseless against the intrusions of unwanted leaders. Leaders' subversive operations can be blocked by stationing a leader of your own in the same region, and you can expel a character from a region by dueling them.
Duels are not literal in the sense that the characters don't start fighting with energy swords, they represent a challenge involving all of a characters' skills to defeat an opponent. Since the chance of victory in a duel is rarely certain, it is important to keep multiple characters on standby to repel any intruders.
You may also undermine enemy operators by increasing your stability (which reduces the effects of their subversion skills), or reducing theirs through counter espionage.
Over all, characters provide a nice way of introducing greater depth to Solar Nations without complicating things too much, as what I've shown above is about all there is to it, but as you can imagine, the implications of some of these new operations are quite big.
Update 1.3 will be coming out in a few days after bug fixing is finished (although I'm sure there will be plenty that seep through the cracks).