It does not really matter who they choose to be the new drummer. Fact is, it will be very, very different, and I do not care if the new guy is Dawson, that Lazarus dude, Simon Phillips, Gene Hoglan or the mailman.
There are basically 3 types of musicians: standard, unique and super-unique. Maiden had the rare privilege of having 3 super-uniques in the band: Steve, Bruce, Nicko.
This was for most of the time a real blessing and was key to their success, but it comes as a curse when one of the super-uniques leaves. We already had that with Bruce's Departure, and no matter how good Blaze was, it was just problematic.
Same will happen now.
It happened in Megadeth: Mustaine writes all the songs, but Nick Menza as drummer was super-unique, and after he left, Megadeth never had that special groove again, despite having very capable drummers. Also happened with Guns N Roses (when Izzy was gone, things were never the same) and many others.
So I personally don't mind the Dawson choice, because in the end it does not matter much. ANY choice would bear the same result: That groove is gone.
If that's a problem or not, is up for everyone to decide. I think, I will not like the result much, but that's okay, because I think Maiden are past the right point of quitting anyway.