The problem with games like this is that players can share code. Decent scripts will be available for everything which takes some of the fun out of the game and makes it less fair to people who do it by themselves.
Nah, sharing code will be awesome. Does sharing code in real life ruin the fun of programming? No, everyone uses code written by other people. It is taking that code, combining it in interesting ways, and adding your own bit of code on top of it that creates really amazing programs (or armies, in this case)
I imagine that depends on how the gameplay works. If there is a "right" answer to the strategy question, then it's a programming challenge and your code sharing objection seems about right.
OTOH if the coding itself is pretty lightweight and the strategy itself is what matters, code sharing might not be a problem. It would also be good for code learners. I think one of the challenges in learning to code today is the difficulty of fining projects where you can get dozens or hundreds of hours using fairly basic programming.
This is where Screeps will be different. You will need to think hard how to adapt someone other's script for your landscape, game environment, creeps setup, etc.
When you share strategies, you still have to manually execute them. Not just copy and paste them into a bot and have it play the game by itself with no interaction.
What fun is a game about coding if you don't actually have to do any coding?