They’re basically putting a square peg into a round hole by drilling out the hole. And then trying to clean up the consequences of that…
Personally, I think it probably causes more issues than it solves… but Blizz did want it to work off the modern Bnet App/Social system with modern anti cheat software and that’s potentially the easiest way of doing those things…
The concerns I’d have involve some of the side effects of the modern client…
Sharding is one of the most common ones brought up.
But the larger concern is honestly lag/latency… A modern client has a stroke when you get 40v40 in wpvp… where as the vanilla legacy client, when run on a modern system that is essentially a super computer compared to tech at the time can push 300+ people on screen without issue. I have rather extreme reservations that the game will run nearly as smoothly as it should on such relatively advanced hardware.
Beyond that, there’s a wealth of small things that all now have to be individually weeded out… Spell crit damage being an example that is critical to fix between the old and modern clients. Textures everywhere showing up unskinned in the demo. Even somewhat innocuous things like water graphics do have a legitimate impact (water uses modern graphics on demo… Vanilla water could be used in pvp situations to conceal your movement, since you where unable to see someone swimming beneath the surface. It’s not a major change, and it even makes more sense to have water be transparent… but it still breaks a known vanilla era tactic.