I was hired to investigate the design and design compliance of a proposed STC modification of a 172 from Lycoming engine to electric motor. Though achievable, the major commercial obstacle was the loss of use of the aircraft while the batteries were recharged - fly it for 45 minutes, and it then sits for many hours recharging. Not good utility, though it seems like this operation has a better than normal opportunity.
For commercial operation, the modification will have to be STC approved (to maintain a C of A). A challenge is that the present basis of certification of the aircraft (and for STC) contains a lot of design standards which would exclude electric motors as powerplants. This should and will change, though a lot of regulatory changes will be needed, and those don't happen quickly.
Electric planes will become practical for some roles, but in the mean time, some battery advancement is still needed. We'll get there on day, and everyone who is trying, is helping.