i have enjoyed playing this on tribble. its not that hard but you can get killed easily if you take your eye off the ball. the objectives are tricky to get all of them, so that will encourage replay and i like the idea of the enemy group changing. that adds a little extra to the map.
i think it would be cool if there were 2 or 3 different map types as well. or even if its cloned and the maps have different effects like rain or snow, or a building or two is moved around.
The way I see it, you'll have to start either A: condensing some of the calendar events, as you did with the Academy and Mirror events, or B: adding a second calendar row, making 2 events active at any time.
To answer jg2112's question, the opponents are selected randomly from any possible race in the game (POSSIBLY excluding Federation and KDF races, though I believe there are separate queues, so it'll likely just exclude the races that are allied with you.)