Are you sure that hole would fit a caliper brake, calipers haven't been fitted to MTB's other than BSO's since the 80's or before.

I think your are going to strugle to get mudguards to fit that bike, it isn't really designed for them, you don't mention any mounts on the fork.

For retro fitting a headshok, if the head tube can take one, it could be done, but from searching for images of the bike, it looks too small & long, also would be a very expesnive option is possible.

Think you need to look at the type of bike you have, and what you need from it, as they don't seem to be meshing at the moment