Whenever I play in the campaign, I always get a team of bots or maybe 1-2 other people with me.
I'd like an option to wait until the team has some more human players.
What do you think?

I actually think there's already something like this.

Go into match settings, go to minimum human players (it may be called something else) and set it to however many human players you want. Lets use an example, say you set it to 8 human players, the game won't start until 8 human players ready up, regardless of how many players are currently in the game.