Oh, I love games with long-term decisions, where mistakes come back to bite you several turns later. Cool idea. The "block bullets with walls" puzzle is very engaging.
If you are interested in further developing this idea, I would suggest forcing players to choose dangerous blocks more often. For example, if you make it in separate levels, you can add a number of blocks to use and beat some score. It will also be a good way to introduce new blocks, btw.