I wonder if the old Traveller rules
Striker would work? It was originally designed for 15 mm. I'm sure it could be converted to 28 mm. It would definitely be able to handle futuristic vehicles. I just checked and the original game is available at
DriveThruRPG and the second version is available at the
Wargame Vault. Not sure why both aren't in the Wargame Vault.