Anything is possible I suppose lol
MR74 has 4 antenna ports. Two of them are for 5GHz, and the other two are for 2.4GHz. The MR84 has dual-band antenna ports, however Meraki for some unknown reason does not offer an antenna that is actually 4-lead dual band connection for MR74/MR84 which ever so slightly kills me inside.
So this would require two antenna from Meraki, or you could get a single dual-band antenna with 4 connectors from a 3rd party like Acceltex for example. (warning - Meraki Support won't help you if you use 3rd party for tshooting stuff)
If you are using two antennas, and if you were to say point the 2.4GHz outside, and the 5GHz inside, I mean...i suppose that 'would' work, although I wouldn't really recommend it. You would probably be better off using two access points, put the one outside with maybe the dipole antenna instead like this: