Time: Having tournament mode get a “Time” aspect to it. Having actions take time, so you as a player have to take time into consideration (resource management), make decisions on which tournaments to enter, how much training to make, and how long you're willing to wait for the market to have certain upgrades/bots you're interested in.
Market: To support this, replace the buy/sell system with a “Market” system, where X certain options are available at certain time, and change as either time changes or other opponents buys/sells bots/parts. This means that if every other opponent have bought a gargoyle, there won't be a gargoyle for sale on the market, and likely will be hard to get parts/upgrades for that gargoyle as well. Similarly bots can be sold/bought with all upgrades intact, which can be a really good way to get into a new bot, without having to wait for market to get the parts.
Tournaments: More tournament types (round robin, single/double elimination, etc) that determines how much time it will take, getting eliminated might give a lot more free time than you expected, either spend time on training or hastily join up to a new tournament, which might make you miss the tournament you where aiming for. Secret characters can take more time, thus delaying.
Opponents: Fight and upgrade on their own based on time. Each time “time” passes (1 week), they get simulated based on their own things. Thus they can win/lose, join different tournaments, get kicked out and such independent of the player.
Goal: Create a more opportunity cost system, that expands on more realistic aspects. Make tournament mode feels less gamey designed. For some players this would likely feel more re-playable.
Disadvantages:
Advantages:
Time
Tournaments
Market
Tournament (Sample)