Hi, as ColorOptimist, I come here because the thumbnail as very cute and good. It's right the double gameplay is cool, and It also reminds me of Ice Climber, its a good base. In fact, I think it would be a good idea to move more towards that style of level design, a vertical gameplay, is not used that much.
Since I couldn't work today, and your thumbnail inspired me,
I made this : 
What do you think? He is no perfect, but he is but it's man-made.
I think it corresponds quite well to your thumbnail and so to your intention. This might be a good fit for you?
In any case, good luck with the rest!