I'd lvoe it if there were a couple different ranges you could practice on that had the legends as targets instead of the current targets. I'd make one range with legends at different ranges without armour, another with legends at different ranges with armour, and a third with legends with and without armour that move. I'd like all the guns currently in the game, infinite ammo, and all the attachments presently in the game. As others have suggested, beign able to pick your legend and have some sort of training area to test them would be lovely too.
A full scale battlefield with realistic loot spawn, AI enemies, etc is unrealistic; that stuff takes resources and servers to run and training maps aren't the priority. But being able to test the weapons, attachments, legends, and warm up your aiming/movement would be very, very nice. I'd love to be able to practice some of my mechanics with the legends without having to be in a real game - like Pathfinder grappling - or see the ranges of different ultimates by testing them, without having to wait minutes to get them in an actual game to waste it instantly. I'd also love to be able to see how the new hop-ups perform myself, and it can be dificult to find or use them in an actual game.
Overall, I agree with what people here have suggested for the most part. I'd like to see a warm-up mode, or training mode actually be useful for more than first-timers, it'd be really nice to be able to play around and practice a bit more without having to try and do so in an actual game where you've got a million other things to worry about too. I also think it'd help with people finding interesting and useful mechanics if they could just go straight to testing, without having to worry about the zone or other people interfering.
