For a more IC wording of the proposal... maybe something like "I would like to put forward to the Federation Council that when assessing the Starfleet's Current Armanent and whether it is suitable for the current state of the galaxy, vessels assigned to Five Year Missions should not be thought of with the same weight as an equivalent vessel outside of the Exploration Corp. The duties of the Exploration Corp are inherently dangerous, and vessels assigned to Five Year Missions operate with minimal, if existent, support. Indeed, Five Year Missions remove those vessels assigned from the Federation's Space, and while they can be called upon to return in an emergency said return is far from guaranteed to occur in a timely fashion. As such, it is Starfleet's belief that the expectations placed upon these vessels in the role of defensive operations should be drastically reduced. With allowance for increased fleet size to account for the resulting loss."
Eh, I'm still skeptical from a game balance perspective. Balancing militarization is one of the defining challenges of the quest system. There doesn't seem to be much benefit in allowing this. I mean, look at what you said:
Long-term, it makes life *so* much easier for us, as rather than losing a Militarisation Point to building a *single* Sovereign for a new Five Year Explorer, we only pick up 6 points of Combat. Feels a lot more natural for Long Term usage, given that I doubt we'll be calling off the Five Year Explorers for anything short of a War.
A little too much easier. We've already seen that exploration missions have big returns. They provide resources and political will when our Explorers are successful. We definitely want to keep as much exploration going as we can, and the balancing factor is that it means if all our combat potential is tied up in that, defenses at home are correspondingly weaker. If we can have lots of Exploration and still have high combat potential at home, it's a no-brainer. Saying that their Combat would count for full when we bring them home and that we'd only bring them home in the event of a war means that there's no penalty, because you know Threat Level would go up massively in the event of a war.