One important issue springs directly to mind - gasoline vapors. To the best of my knowledge well pumps are not explosion proof, and if you park vehicles in the garage you will have fuel vapors present - whether you smell them or not.
Other than that consideration your other concerns are minor. Enclosing the units will hold heat in (be careful in warm weather) and if sweating of components becomes problematic drip pans can easilly be fabricated and installed as needed.
Gregg