I think a lawn-mowing game would be cool.
A lawn-mowing company simulator.
You have to manage work hours, figuring out how to be efficient and saving more time and money while mowing, budgeting gas and upgrades for your mower, managing schedules, clients and balancing budgets to make a profit off of it.
You have the entirety of the in-game summer vacation (90 days, 20 minutes per day) to reach a set profit goal of $200+
edit: also make a new game plus where after you reach the profit goal, you have to survive the zombie apocalypse by cutting grass and upgrading your lawn mower to fight off endless hordes of zombies. In this game, you struggle to mow lawns, survive the apocalypse and find survivors in the tall, tall grass.