I'll start. I'm working on a top down roughly ww2 era RTS. I have two main gimmicks:
The first one is that the front line is persistent, allowing you to start a battle whenever to advance/skirmish/capture equipment/whatever, or be forced to defend when the enemy decides to attack. You're squads will be where you left them allowing you to prepare defenses in advance and having to think ahead of how the situation can change (and be forced to improvise when it does).
The second gimmick is that you can design you're squads as you want. You can for example spread out smgs so that all squad leaders have one, improving the close range firepower of all squads. You can also give all you're smgs to a single squad, making it excel in close quarters, but limiting its efficiency at range and the close range efficiency of other squads.
I want the player to solve their own problems, if they are facing tanks then they can raid the enemy at night and try to capture an At gun, or they can position themselves is forest where tanks can't reach/are vulnerable to infantry.
I feel ya, the only thing keeping me to this project is that I am building it in Java, and I am a Java developer professionally. I am able to create progress reliably and have the tools to get things done. However before this I must have atleast 20 projects that I forgot within a week.
My only tips is to work with tools you are comfortable with, and lower the scale down a lot! Like really a lot, you should have something that is playable within a week, else you'll lose motivation.