Reinforcing things like gear blocks and firewalls and wing mounts are not done for crashing, they are done to avoid them breaking in flight. If there is no triangle stock on the wing bolt blocks and they are not put on perfect, they have force on them every time you pull up or push down and will eventually let go. Gear blocks that are just kind of glued in will rip out on a rough landing instead of staying in. Firewalls coming out when you are starting the plane are really dangerous. If you put in the triangle stock, it will make that not as much a possibility.

If you crash and it takes a bigger chunk out of the fuse because of it, so be it. Don't plan for better destruction in a crash, plan for it staying together and chances of it coming apart in a light crash will not be as high either. If you under build, you will be fixing more. If you over build, you won't. If you crash, you have to fix either way, so fixing an over built plane may have less to fix than an under built plane.