With all the hack and slash games found on the market today, this should be a welcome change.

Not sure about the ants eating leaves though,.. in real live ants bring leaves back to their nests where it is used to grow some kind of fungus.
Perhaps caterpillars would fit the bill beter. In terms of 'fighting', it would make more sense as it would be perfectly okay to have one or two of them in your garden. Ants on the other hand usually go in groups, especially when food is involved.

Please do, keep the ideas coming. I'd very much to like to see what else you've planned.