As for the matter - if IC pulls out of Rheinland it will lose money, and a lot. If the tides won't eventually be in their favor they will be the ones who will get harmed harder by it.
They will lose a whole market, while if Rheinland does manage to somehow recover I expect that the gap in the market IC left behind will be filled by someone, and with that big market, that someone would become an actual competitor to IC. On the long terms this could be IC's downfall, if the future don't play to their will.
However, IC funds huge parts of Rheinland's economy, if they pull out, with the war against Liberty and the expansion of Hessians, this could, to say simply, crush Rheinland's economy, leading to upraises in Rheinland and generally chaos. Even possibly a Hessian take-over. (Don't forget that Hessians are the 3rd largest criminal group in Sirius, they have huge numbers and are an actual threat to Rheinland.
If IC pulls out, Rheinland won't be able to fund both fronts - Omegas and Liberty. They will have to choose in which one they want to cut down.
Also, with the high number of pirates and criminals in Rheinland lack of insurance may lead to Rheinlad being cut-off from parts of space since no one will fly there without having his cargo insured, and Rheinland is low on many essential resources for the war.
TL;DR
Rheinland is a house - it holds a lot of power, the biggest one is people.
IC is the biggest financial body in Sirius - filling a huge hole as IC can leave behind it is nearly impossible, especially in the state of war.
![[Image: p2SKLap.jpg?1]](http://i.imgur.com/p2SKLap.jpg?1)