If you have a chance to be on the team to fly in Bulgaria, don't let money stand in your way. In 2014 you might not have the opportunity to compete and if could be an even more expensive trip. In FAI business, opportunity doesn't always knock again.
The FAI doesn't care about citizenship, it's a matter for the national aero club (AMA) to name the team. The only rule is: You can't fly for one country, then fly for another two years later, you would need to sit out one cycle.