Single wide or double wide? Mobile/modular homes do not have to follow the same building codes as traditional housing. The construction is designed much lighter, since the home must be moved by truck to the site where it will be used. And the wheels/axles used are designed into the initial construction and are industry standard.

The usual type of stucco most folks know about is heavy sanded material applied in three coats. It contains sand and has to be applied over a wire fastened to the building. Look at a polymer stucco. One coat, lighter, but more expensive.Polymer stucco

Mobile home walls are thinner than stick built homes and are built with lighter materials. Plus, the ceiling/roof does not usually have the bow resistance design of a stick built house. Heavier wall material will cause the walls to bow out from the weight.

The problem with mobile home AC/furnace units is the physical size and design. And the number of manufacturers. The problem may be the physical size of the area in which the interior unit is mounted. If that area were enlarged, a larger unit could be installed.

The biggest problem with flooring in a mobile home is entry/exit door clearance. Very often, the entry doors have metal doors and very thin thresh holds. The doors cannot be shortened and the flooring height is very limited to be thicker than the original height. Some brands use sub flooring materials that are very susceptible to water/moisture damage. Those materials are often glued in place and quite labor intensive to remove.