ok firstly the manhunt would nearly be impossible without some kind of radar system, soon as the hunted is lost it would nearly be impossible to find them on such a huge map. However I do think the normal radar would make it too easy, I was thinking about gta2, which had a similar gamemode. It worked with arrows pointing in the direction of the player, like a compass, maybe a distance in metres too would help. To be honest there are alot of cool features that were in gta2 that would be a great addon for mta (oil slicks, car bombs, mines) but as I see it the mta team have enough to work on atm anyway.
Also I dont see why everyone should respawn back at the mansion, why not just make the person who got the kill be the next person in.