A few issues with bringing Blaze and Paul out on stage
Dianno can't really sing anymore and is in a wheelchair. Dianno probably does not sing his maiden tunes in the original key anymore.
Blaze in the 2000s grew to be twice the singer he was in Maiden. Consistent great live performances etc. I actually think he's (only) slightly lost a step now, vocally, after the heart attack (saw him live recently). Hes still good though.
However if Blaze came out to sing say, Futureal, well Blaze sings that in D nowadays (given aging and it fits him better) and Maiden would do it in E. So that might once again leave Blaze in a Maiden show not quite at his absolute best.
I guess they could just transpose it down the neck to D from 7-3-5 to 5-1-3. They did similar for Bruce on lord of the flies