I don’t think it would be safe or legal. When you search tow capability it comes up at 750 to 1100 kg which would barely cover the empty trailer never mind a 500 kg horse and tack . It wouldn’t be able to stop it especially on a slope and would be unstable .
My friend tows with the kuga
( tow capacity of 2000 kg ) and one pony feels the top limit for it. Sorry!
It wouldn't be safe. My single horse trailer weighs 750kg on its own. Add on a 500kg horse and you would be way over the towing limit. My sorrento has a limit of 2800kg and have been in situations where that has struggled