Training Gamemode

I would love to see a training mode added. I often want to try out new teams, or just see what works against what with what I have. As of right now, I use the galactic challenges as a "training mode" so to speak, but it is heavily inconsistent with the characters you fight against, not to mention it having modifiers so I don't get a true reflection of how my team fares against an opponent. A training mode could have different tiers of characters as well (with selectable gear and relic levels), which would be perfect to pit some of my lower-geared toons against a team of a similar power level. Just a thought, but I think it would be really cool.