We anticipate most users to create their own meta units. 

Here are some of the current ways you can do it but we hope to get feedback on other ways:

1. Player selects units, right-clicks on another unit to have it join that meta.

2. Player selects a unit and has units constructed and sent to it to join a unit.

3. Player drag selects a bunch of units, creates a control group and units not currently in a meta unit are put in one as best the game can (non ideal but better than nothing).

Other things we are considering but are not promising (scope cost) are being able to design meta units outside the game and then being able to, in game, select a unit and choose a meta unit design and have the types of units that have been considered show up as icons that the player can select and have built and/or unassociated units attach to.  

I consider an ability to design environment-reactive formation tactics as a critical element for meta-unit success. Without this, meta-units will be like formations in Homeworld, BfME and other games: useful, but not groundbreaking.

Let me echo that this game looks amazing.  In fact, I signed in for the first time here because of how awesome it looks.

I also think that meta-units are a brilliant and also critical piece of making this game's gameplay enjoyable.

My ideal would be for you to be able to define the composition of your meta-units prior to entering a battle based on the units you have access to at the time (similar to defining what units compose a battalion prior to fighting in a real war).  In battle, you could then assign to the general production the building of a meta-unit, and the factories would smartly dole out the production tasks to build the unit.  Should individual units in the meta-unit then be destroyed, the factories would then automatically replenish those units to restore the meta-unit to full strength without the need to micro-manage.

The game would then ultimately revolve around actual meta-unit battles composing the war and whether your unit composition and management of meta-units was appropriate for the scenario.