From a design perspective, I feel the idents represent Wales well (even though I'm not from Wales!) and work nicely. I can see the similarities to BBC Scotland and they both tie together nicely.
From a technical point of view, would there be a point in keeping BBC Two Wales running and having this as a "major timeslot", as you phrased it? As well as this, I don't think it would make sense to hand over to the NC as BBC Scotland doesn't do this and there would be some continuity between the channels if that were to happen. Same goes with the national anthem.
Other than that and the other points mentioned by my peers, keep it up as you've got a great mock!
My tweet was read out on BBC Four's Eurovision coverage and Rylan Clark-Neal replied to it. That's all.