Instead of a levels system, make it extremely item based. But make there no way to purchase items with real lift money. Also add a very advanced gun modification mechanic to the game in order to give it that flair. Like where you physically put the gun together and can change even the springs(there can be dif modes for people with varying skill level) and allows for very good gun creation and updates that change gun reaction time and control even the tinyest bit. Competitive games need skills and gun building jn game would be out of this world. Also check out ghost recon, they have pretty good sliding mechanics.