Alright, as the developer of Oki I'll give my opinions on this;
Yes, I have said GMG were in debt to Interspace, but I did not mean that they were in debt in the way where they have to make regular payments for a loan. Interspace financed the building of Okinawa. GMG set up its design according to the one given to IC to approve of (this isn't written in RP, but implied, as IC would never agree to finance a system-wide construction effort without having some kind of written design plan), and then gave IC the monthly/yearly/whatever period expense report, at which time IC would then pay those bills, sans any expenses resulting from something being done that was not a part of the approved plan.
The "debt" GMG owes is that they must give IC a 5% cut of their H-fuel profits. Yes they are in "debt", but the way of paying it was decided on before construction began. There is no total sum they have to reach to "pay it all off". It's an indefinite cut of the profits from H-fuel sales made from the Okinawa clouds. Note the word indefinite. This is the loan's principle, plus interest. It is what allows IC to continue to make profits from their investment. I chose this instead of a simple loan that must be paid off with interest, because the construction of an entire system is a MASSIVE investment with a LOT of risk. As such, Interspace is going to want a kind of payment that would be in line with the amount of risk they take in financing. In the long term, a cut of H-fuel sales for the rest of Okinawa's lifetime of mining, the ability to set up their own station in Okinawa, and the ability to hold H-fuel on their station, as well as ship it, was a better profit than getting their loan repaid in plain credit form.
Personally I would see Interspace valuing their station in Okinawa above their cut of the H-fuel. IC| can of course see it differently. However, I imagine the station as a sort of free-trade port in Okinawa. Fujisawa is for H-fuel. Isehara is for terraforming and holding mined Plutonium (it's a factory in .86, so it retains a specialized purpose). Furyoku is the only station that doesn't have a specific purpose, which makes it more suited to be able to handle the importation, distribution, and storage of all other commodities. GMG personnel have to eat, where does that food come from? Probably Furyoku. If Okinawa is the Omicrons, Furyoku is Freeport 9. It's in the middle (and is in the middle of the system, with great market location), it handles all sorts of commodities, it handles storage, services, bars, entertainment for the system's residents, etc.
Hope this helps clear up some questions.
Note to IC: Holding GMG in default doesn't really work. However, closing Furyoku to GMG pilots and other personnel, could really hurt their morale in-RP. Fujisawa is a mining and military base. It certainly doesn't have a lot of entertainment. It'd also allow you to prevent the GMG from getting food and other commodities from you, making it much more expensive to have it imported from long distances in smaller amounts (they lack the pure storage room of Furyoku), and more often. It'll hurt your financially as well, but it'd hurt them more.