Modding multiple shipyards per planet?

[Suicide Junkie]

As long as you can convince the AI to try and build the expansion project first.

If both the expansion and the upgrade have the ability the AI wants, the AI may end up trying (and failing) to build the upgrade facility from scratch.

If you want to limit the number of expansions, you'll have to find yourself an unused ability that the AI checks for the ability amount. Giving the expansion a higher ability amount would encourage it to build the expansions instead of the full yard, and then "upgrade" to the facility with a lower amount of the ability.