While I think it's a fair argument to make the specific geography of the Mississippi makes it easier to operate with numbers, I still don't think it's a good option. Mobilizing large numbers brings a substantial financial burden to our state, while also causing diplomatic friction. States generally don't want large numbers of troops passing trough their backyards, with the fear of those troops being used against them being especially high if the diplomatic relationships are fresh and thus have lower trust. The fear and the anxiety about armies raiding for supply causes a lot of friction, which hinders our progress to our ultimate goal (safe shipping trough the Mississippi) by damaging our diplomatic capacities. While using large numbers of troops is militarily effective, it causes friction every time we do it and is thus strategically undesirable. And that is aside from our need to project power in places less good for supply than the Mississippi, namely any place else that isn't connected to the great lakes.
There are two aspects to this.
One is the budget requirement. The other is the diplomatic implications.
...
As to the diplomatic implications, the Devil Brigade doesn't have a magical "zero diplomatic impact" modifier to bypass the effect of moving troops through other people's territory.
Imagine the following conversation:
RCS Mayor: "So hey, if the Commonwealth were planning to drive up to our city on a pretext, camp out by the city limits in the middle of the night, then stage a raid, depose our leadership including me, and install Commonwealth puppets who wouldn't play hardball in negotiations with them, who would they be sending to do that?"
RCS Chief of Staff: "A group of specialist troubleshooters with Old World equipment and enough training and firepower to bust open a whole Victorian division by themselves. We wouldn't stand a chance. They call them the Devil Brigade."
RCS Mayor: "Now, it says here that the Commonwealth is sending troops to attack those assholes to the south of us who didn't respond to their ultimatum and are still harassing river traffic. And that the troops they send, uh, they're going to be passing through."
RCS Chief of Staff: "Yes, ma'am. They want to camp on the city limits one night next week."
RCS Mayor: "Right... which unit did they say they were sending?"
RCS Chief of Staff: "A small, crack unit called the Devil Brigade."
RCS Mayor: "Uh. Eh. Eheh. Eheheheh...
Oh shit."
...
While sending the Devil Brigade might
in some ways have less diplomatic impact than sending twice as many troops from the rest of the military... the Devil Brigade has a reputation, too. Among other things, a reputation for spending thirty years as a bunch of scavenging ruthless hardasses, and for being very dangerous in battle. That reputation may cause a diplomatic kerfluffle that sending, say, the Blues Brigade or the Abraham Lincoln Brigade does not, because nobody's ever heard of those guys and they're not emotionally as scary, even if there do happen to be more of them
I'm not saying the diplomatic angle doesn't matter, but it's not as one-sided as you make it out to be.
Furthermore, experience will
rapidly show that Commonwealth armies along the Mississippi
don't need to scavenge, for the same supply-line reasons I already discussed. We
have the
Professionals Study Logistics national spirit, and almost nothing could be easier for us than maintaining a supply line down the Mississippi. Much easier than maintaining it around the north shore of Lake Erie during the Erie War, and we
did that.
...
Then there's the budget question. Frankly, the problem there is that the cost savings of deploying a smaller expeditionary force may very well be offset by:
1) The cost of needing to compensate for just not having as many warm bodies in the expeditionary area.
2) The cost of maintaining any unusual equipment the Devils may have (even including stuff that isn't strictly OWE).
3) The cost of us needing to hire extra foreign trainers to compensate for
not having the Devils available to do
that- remember that the Devils will only be on deployment a fraction of the time, but we'll need to keep the trainers on payroll
all the time.