I still think that there is enough squads for mages to join. I mean, my character can only join two squads too. "Dragoons and Grenadiers." Mages have a little more strict, but they got two squads they can join as well. Being a Marine is just like being a normal soldier except you have the luxury of being the superior force on sea. The way I see it is you have three good choices. Stay a guardsman and have no restrictions, Join the navy and not force your char to love the sea, or get 50 hiding and like 70-80 stealth and join the scouts.
I don't hate your idea. I just think it's the wrong time, you have the same amount of choices as everyone else does, and Warrior-Mages would be more Covian than pure mages. Plus it's an awesome temp if you use it right.
I'd make this

100 Magery
100 Evaluate Intelligence
120 Swords/Fencing/Macing
90-100 Healing
90-100 Tactics or whatever else.
100 Anatomy
100 Meditation.
90/90/70
It would be good because if you got disarmed you have 110 Evasion on your back. With your weapon you'd have 50% chance of getting hit by a person with 120 weapon skill, and like 43% chance of getting hit by a GM weapon user. You can heal 4 different ways, cure poison 3 different ways, and kill someone in like 2 seconds in a duel. Just seems like this would be a good fit if the mages used a weapon as well as magery.
I'm out peace.