Mecha are a real possibility but it’ll take lot’s of resources to accomplish the goal of making mecha a true reality.
Sure, Current construction vehicles do the job but mecha that are designed properly & effectively would be much more versatile. For a simple example, A humanoid form would be especially useful in construction projects on uneven terrain.
The feet could brace a mech so it’s arms could hold a buildings wall steady while another mech connects another side of a buildings wall.
It’ll take a truly responsive man to machine interface for mecha to be useful of course but it isn’t impossible.
Of course it’ll take plenty of testing with prototypes to ensure that mecha are indeed worthy of creating & maintaining but it’s a worthy undertaking!