Hi,
Wonderful idea for a game concept, As i just attained a certificated in music prouction for games i'm very eager to get started on some projects. If you'r interested i can send you some examples. As far as interactive music involving stems etc we could discuss this or if you're looking for 5 minutes of one piece that simpily loops every 5minutes of gameplay this would be a far simplier option but can cause listening fatique quite fast. Hope to chat more, good luck.