I'd recommend that your group avoids the seemingly easier route and instead steps outside your comfort zone to give "vanilla" or as-written Alliance at least a couple tries before trying to force your character concepts on a game system and role-playing environment that may not be compatible. This is not just theoretical advice, Alliance has been around for 25+ years, so this type of thing springs up from time to time and the experienced players posting in this thread have seen this before.
Each chapter has its own unique in-game geography, main conflicts, and other rich and highly developed histories from years and years of actual player experiences. For example, while the Southern Minnesota chapter plot has royalty, guilds, and that political structure in the background (far away at the Capital), and the adventurers (players) are usually on the front line in a hundreds year old war against cursed creatures called the Corrupt, expanding deeper into war-torn enemy territory each year.
I have had personal experience working with a group concept similar to the one you are describing. A few years back in Minnesota, we had a large (dozen or so) group of friends join the chapter with the intention of being their own group with their own pre-written background and character concepts created before consulting with chapter plot staff, including being from a land that did not exist in the storyline of the chapter and some other minor issues that were in violation of Alliance rules. In short, it was a very difficult task to try to reconcile the differences for friendly customer service reasons, forcibly educate them on Alliance rules, and convince them to join the storyline already in progress. However, in the end, only a couple players stuck around after a few games and even those players abandoned their original character concepts in favor of Alliance-compliant ones.
To summarize my point, rather than adapt characters from another game to Alliance, start new and fresh in Alliance and create characters that are built for this system. If Alliance is what you're looking for in a game after trying it out, great! If you try it and decide it's not for you, that's cool too. But again, give Alliance as it's been played for many years a try first.