Yeah, the string is a problem. I spent at least 60% of the jam working on it, and got it to be 'stable', but it's still pretty jank.
It 'weighing down the characters' as you put it is due to me fixing issues caused by both of them moving at the same time(specifically them moving away from each other, and falling with the string suspending them in the air). So, when both of them are moving due to user inputs, the center node of the string only moves at half speed.
The level design vs the control scheme is uhh, something I don't think any of us thought of during the jam, but is certainly a good point!
And yeah, as a proof of concept, we on the team think it has great potential, but we also agree that there's some issues that would need to be ironed out to truly flesh out the game.
Thanks for the feedback, and I hope you enjoyed playing (even if you couldn't beat any of the levels)!