AOB, TCW, TOS, the songs are comfortable to sing. Bruce (and Roy Z) knows his strengths and limits. He is properly produced, sings in comfortable range. In my mind, the biggest problem is HOW Maiden albums nowadays are produced. 'Live in the studio', 'will be fine how it is' and so on. The Band (with Steve at the helm) feels too comfortable. They need to challenge themselves. (Let's make Empire of the Clouds with real orchestra!) 'Tough guy' producer would be 'kick in the ass' for them.What solo albums? You mean these songs that were recorded 15 to 30 years ago? DUH!
Priest chalenged themselves with Firepower. 'Let's hire this modern producer and on top of that let's hire Tom Allom.' Those two had suggestions for Rob (regarding singing), I'm sure you have read interviews.