That's how they they did the codemasters EU to Turbine US server transfers back in the day, which created some tech headaches for them in 2025 BTW.
But they did not and will not do it that way this time -- for one, they want to start those servers with cleaner character and other databases.
Most importantly, a huge part of the incoming transfers will be to allow people to choose whether a) they want to stay put for the time being, b) transfer to a Las Vegas server, or c) transfer to an Amsterdam server. Or indeed mix'n'match between those solutions on a per-character basis or whatever.
The big problem that occurred with the 2025 LOTRO transfers, apart from the hardware and tech that they had at the start of the process being completely inadequate until they started upgrading it starting in the second week of it all, is that the players had overly few new 64-bit servers to transfer to, so that the main US server is close to maximum capacity, and the main EU server has exceeded maximum capacity. Bearing in mind that the devs didn't even know what exactly that maximum capacity was until it was actually reached on live.
The first of those issues DDO will have dodged because the hardware and configuration matters that created it originally have been solved. But I am sure that SSG is now expecting a much larger and longer transfers process for DDO than was envisaged (LOTRO had many, many returning players plus a surprising number of new players plus they had massively underestimated the sheer quantity of alt toons and alt accounts), so that more new 64-bit servers trather than fewer seems likely.