Projects are pretty good in this game, as they help provide you with some boost, to military, income / resources and defence. However, one thing that's bothering me is the 5,000 infra per project. For small players this will be easy to reach as alliances can provide them with aid, but as nations grow infra gets more expensive, so it's much harder to purchase a project. Also, some projects cost a lot, like Vital Defence System.
Instead, what I suggest is for the 5,000 infra to be scrapped, and be replaced with "1,000 infra per level". Instead of waiting till 5,000 infra to purchase 1 project, we can make all the projects have 5 levels. For every level a person buys, a person will get 20% of the benefits for the maximum level. (Eg. Lvl 1 of Iron dome gives 10% of shooting down enemy missiles, while lvl 5 gives 50%). This encourages more people to purchase projects, especially different ones. The project costs per level will also be cheaper, so more people can afford to buy 1 level first, and purchase an upgrade to the second level at a later date.
To spice up the game, maybe a future upgrade where ships / missiles can destroy projects and prevent the person from building another project for 14 days might let more alliance have their members produce missiles / build ships.
Hope to hear some constructive feedback about the idea.