Are the three carports shown as parts of three of the lots? Is the fourth lot shown as having a parking space on the driveway, but not a carport?
I suggest that a general meeting could resolve that unit owners may install garage doors within their lots at their own expense subject to (some sensible conditions such as their style or colour or whatever matters in the context) and subject to agreeing to be responsible for their repair and maintenance.
If the fourth lot could have a carport constructed over its space, perhaps the resolution could also grant permission for that unit to construct a carport (at its own expense, responsible for repair and maintenance etc).
If each unit owner would be just doing something at their own expense, within their unit, with permission, then the money need not go via the OC accounts.
However, if the 4 parking spaces are not parts the unit/lot areas and instead are common property, then perhaps nobody has a valid claim over the covered spaces. If that is the case, perhaps the OC should look into validly creating and allocating covered parking for all units?