The mod tool is cool and all, not enough of those nowadays, but with it, you still only run and shoot, just in a custom map. In Crysis, you can choose to turn invisible, have super strength, speed or maximum defense to best suit your combat situation. In BF you have destruction, vehicle combat, in TF you have class variety, and in Tribes you got a ton of cool gears in your arsenal. In cod, it's just cover, shoot, kill and repeat. Rekoil looks to be the same way. I hope the mods tool are good enough for modders to create something great out of, like they did with DayZ.
P.S.: I think the formula for the best shooter ever is in each of these games. Class variety and teamwork from TF/BF, wanton destruction and vehicles from BF, a good arsenal of gears to tip the odds in your favour or counter your opponent's gears, a good selection of weapons (always the hardest part, it doesn't have to be big, but there shouldn't be one overpowered weapon) and individual abilities/mechanics like Crysis/BF.