Today the official Twitter account of Metal Gear Online (Metal Gear Solid V: The Phantom Pain's online mode) gave an interesting piece of information about a newly announced option for custom matches:

The team also clarified that there won't be options for odd number of members per team, and currently there are no plans for bots.

A custom match option is definitely rather handy if you want to play with smaller teams to test indivisual skills. Ultimately, more option are always welcome. Too bad for the lack of bots, as those tend to be useful for self-training.