I’m about in the middle of this as I can be I think. I see pros and con’s to both sides of the debate (I might lean a tiny bit towards the against, but trying to stay neutral in this since the transfers are now a confirmed thing coming). It also sounds like it won’t be here for a few months, so things could very well not be finalized.
So with that, here is how I see it, and my suggestions. I invite others to leave their constructive suggestions here as well.
Pros for Map Transfer
Allow existing characters people have played with for hundreds, thousands of hours even to continue their story back and forth
All that hard work of trying to get that very special weapon you RNGed the living crap out of to finally get it, won’t have to be redone from scratch
As a single player only person, I would benefit and enjoy this more myself.
Cons for Map Transfer
Pay 2 Win (for once, I will use this term) as it could allow players to hide on Siptah from people who don’t own it, return stronger and bring various advantages with you.
Exile Veterans can have a major leg up on the content in Siptah, negating a lot of the challenge of it (not to mention the PvP challenge).
Various imbalance concerns, most of them being related to item transfer
Story wise, it makes no sense. I realize it’s a video game. But there is no logic to it.
Thus, here is where I would suggest some limitations
No transfer of items, save for what the character has equipped and/or on the hot-bar
No Thrall or Pet Transfers
Limited to time. You can transfer, but you can’t go to other servers for 15 days (thus, causing whatever you have to decay on the other map). Or some other number, just something that makes it so you can’t do it frequently.
Require various objectives be completed first before being able to transfer to and from. For example, on the Exile Lands, maybe you have to complete the bracelet quest in order to leave the Exile Lands and find yourself in Siptah. Or a new quest, where you escape in one of the portals that have been opening up on Siptah.
Any of the above limitation suggestions (and others) be configurable for Private Servers so Server Owners and Admins can set it how they want to best fit their needs of the server.
New character cut-scenes and/or backstories for when you transfer so that it makes at least a little bit of sense. Examples:
You escape the Exile Lands (via portal, or completing the map campaign), but are shipwrecked on Siptah, losing everything but the clothes on your back.
You escape Siptah via one of the portals that have been opening up all over the Island, and now find yourself in the Exile Lands. You had to flee on short notice, just managing to leave with only what you were carrying. Now trapped, you find that the bracelet you had found yourself with on Siptah is now activated, and trapping you on the island.
Imo it would not be that troublesome if you could not build in siptah, but the way it is, most DLC users would simply build their base on the other side and have their raiding spree in the exiled lands.
Perhaps if only DLC owners can play on siptah servers, this problem wouldn’t exist anyome, since every player online owns it.
While I certainly plan on starting a fresh Siptah game when I’ve finished up the last couple of things I wanted to do on my current game, I can also see an appeal in being able to hop back and forth - go off on a few new adventures with old characters and followers. But equally, I can see how potentially damaging it could be outside of the single-player environment without serious limitations being applied. Your suggestion that all factors should be configurable (presumably up to and including whether transfer is possible at all) would certainly seem the most logical way of achieving the best possible outcome for as many players as possible (which of course also assumes that the programming side is straightforward…).
One slight dispute - you suggest transfer would make no sense storywise, and yet yourself suggest a couple of perfectly logical ways the story could still work. It really is only the intro scene to Siptah that would even be in conflict at the moment. The Exiled Lands are impossible to place in the context of the Hyborian Age (the Outcast is right, none of it’s real ) - the Lemurian, Khari and Stygian lore all fits with them being in the right locations, with Sepermeru in the west and the jungle in the east, but then the sun, moon and stars are all wrong - so whatever is going on, the Exiled Lands are in at least some way outside the normal rules. With only the slight adjustment to the intro that you propose, the story would already be fine.
And perhaps to explain voluntary transfer back and forth with more power, you could be free to travel (by portal or ship (since apparently ships can carry people from Argos to the Exiled Lands, passing near Siptah)) once you’ve removed the bracelet (perhaps with the penalty of no longer being able to use the Obelisk system when you are in the Exiled Lands). And maybe some corresponding element that would have to be completed on Siptah - such as learning to control the surges - that allows you to freely leave the island and return, having learned to overcome the storms. Of course, all of this idea could only really apply in singleplayer games and some private servers, too much potential for abuse elsewhere. I guess the real point is that I enjoy the lore and like the idea that there’s plenty of ways the story elements can fit together.