Since you can't transfer characters this is my suggestion.Create new chars of the same level of Nova ones that must be transfered ("template" characters) based to level they will get basic rewards.
EXAMPLE :
A player level 90 will have in his new trifri char full NM/Terror MG set (both) +0, MDC weapons +0, a fluid +0, some lant coupons, other various items, 3 MONTHs premium, and try to refund all the item malls too. You know, like 69 box...but it will be based on char level.
This is ridiculous!!!! So Nova players will get all their items +30 deleted so Trifri can easily kill us in pvp? NO THANKS. This will result in all Nova players leave the game (so server merge would be useless).
My idea would be: without announcing in advance set a date in which duplicated items cannot be traded (if they are on the same cloned char - easy to find on dev side), so:
- Nova players will choose which character keep (if duped): Nova or Trifri. All the items on the same char will be bound till the end of merge, and one of the 2 characters will be deleted), so at the end Nova players will basically have their Nova (or Trifri if they prefer) characters moved on Trifri and the cloned one deleted without any chance to transfer items to other accounts. In this way there won't be any chance to get profit.
- For PK/PVE: I woul add a system to choose at the login PVE/PK, then you will be bound for 1 day (so no chances to get it on/off every 10 seconds)
- For PK: other than what already suggested like race, level,... I would also add a limit to kill the same player, like 10 (e.g. player A cannot kill player B 100 times in a row - after 10 times in 1 day, that players won't be anymore killable).
- Before implementing PK protection or anything be sure there won't be any problem to join party (like it was with pk protection).