The planks being permanent was the plan for the design; I wanted to have something where you build your own structure and have to plan ahead with various randomized shapes to build a tower up the cliffside, and each time you reset your run, there would be 1 of a set of modifiers applied (gravity would be rotated 30degrees to either side, your character would grow with time [you build as you scale up ;p], door objects would lose collision [they opened], etc.) and then there would be a few prebuilt blockades higher up that you'd have to build around.
The timer was originally there to prevent the player from just placing blocks underneath them for bonus height, but the build distance limit made up for that and it turned into "get the high score in 60sec, and you build the fastest path up but need to ensure you can get back up after you restock at the base"
If I had the object variety, the timer limit wouldn't be as needed, but I did want to make some limit to how high you could get to have a material goal to play again