Part of me wants to stick to the AEG Spycraft line that levels do not have to directly correlate to the station of a person (for instance, Presidents are ~16th level, Senators ~13th, Mayors ~7th). With a bit of story, a 2nd level fighter could be a fine General if (big IF) he's got the skill sets to make it work. A human could double up on the Educated Feats to make Knowledge (History) and Knowledge (War) class skills... then max their ranks and still have two bonus fighter feats to put him above your average conscript or soldier.
The other part of me however just has to ask "if level 2 = former and potential renewed General, what will level 18 mean!!!" Will this player, who already is pretty much in the upper echelon of this continent's ranks of military leaders, want to go further up the chain in his career? Seems there's little upward mobility left, and that's usually a good part of a campaign. Being self-exiled is an easy set up for "I return, am welcomed with glorious sounding of trumpet, and retake my position" stuff. Furthermore, if he's level 2 and a military general, how will this impact his wealth and political pull? There really is little reason he couldn't walk into the armory, tell the guards to take a break, and walk out with all he could carry. Heck, he wouldn't even have to trick the guards- he could have it all delivered to his personal tent set right in the middle of his nicely guarded military camp. Also you'll have to deal with the reprocussions of his greatness as a level 2 character in the campaign with your own adversarial armies... if he's level 2 and was the best- he's in his right to be confused when you've got simple guards matching him sword for sword. Did he just get rusty? I pretty much figure that this sort of stuff is like riding a bike- you don't lose levels upon levels of competence over the span of years.
On the whole, I think he's asking for a lot more than simple status- even if he doesn't know it. You'll have to warp the entire campaign reality to suit his purposes. Furthermore, it'll create massive inequity in the relative status of the party members... level 2 rogue pauper-ish thief, level 2 ascetic monk, level 2 acolytish cleric, level 2 hedge wizard.. and level 2 Grand General of the Grandestest Grand Army in all the Lands Fighter.
Doesn't seem to be feasible as far as I can tell. Too much, too soon- with too little to strive for. Generalship is a great goal. Not a great Start, or necessarily a great past.