Hi Brian,
Joining IGA is simple and details are on the first page. Here is a general overview.
-Have a safety rating of 80 or higher (easy enough).
-Routes can't be overly expensive or cheap from the standard price (+-25%)
-Routes can't be impossible to complete (landing on a short grass strip with a 747, flying from San Francisco to Sydney in a DC3, etc.)
-Follow FlyNET rules (we all have to

)
-Finally, place an assigned IGA sig in your signature. Then just type INTERCONTIENTAL GLOBAL ALLIANCE MEMBER somewhere in your airline mission box so other members can easily identify each other.
The requirements are pretty simple for a reason. Currently FlyNET doesn't have an integrated alliance system (maybe FSAirlines will one day), so there isn't much of a reason to limit airlines based on their flightplans like in the real world. All IGA is trying to do is to form a group of airlines with mutual agreements and partnerships, like a flight club.
As for your flightplan, the only other airlines servicing North America are North Airways and Air Mermaid. North's flightplan is mostly concentrated within the US with a couple routes extending into Canada, Mexico, and the Caribbean. Air Mermaid is centered around Jamaica and the Caribbean with a couple routes extending to the US and South America. Canada is pretty much empty for now, so your 500 or so routes should have a minimal impact on our flightplans. There may be a few conflict routes, but I'm sure that can be easily worked out and turned into codeshare routes.
It's completely your choice if you want to join. If you do, just send a message or just post right here
As for the signature, I'll see if I can get the IGA text changed. You're right, it is a little too bright on a bright background lol. I can see why the blue suits Arslan. All you can see after departing from Kingston is water.