Well, Blaze for the most part has done his own material (with a few Maiden (and Wolfsbane) covers in the set, but again, 80-90% his own material). It's always seemed to me that he's very much about the fans, and that may well be why he's doing this tour. And, Di'Anno has stated intention to retire soon, so it's not as though this partnership will be long-term.
Personally, I'm a little disappointed that Maiden (seemingly) never asked Blaze to open for them. It would have been a much-needed boost for him, and it would be awesome to see Blaze and Maiden on the same bill.
My point is, if you are familiar enough with Blaze's post-Maiden work, I'm not sure how you could possibly interpret anything he does as leeching on the fact that he is a former member of Iron Maiden. I mean, he plays Maiden covers, but think about Dio playing Sabbath and Rainbow songs long after he was no longer a member of those bands. I'm sure no one would accuse RJD of leeching on the fact that he used to be in Black Sabbath. The only other way I could figure, given Blaze's entire career post-Maiden (this tour is the first time he had ever done anything IM-centric), that you could construe him leeching on his Maiden past, is putting his name on his band. But that's really something that just made sense in some ways, since he was always the only member of any of his numerous bands with any name recognition.
I don't think there's anything leech-like at all about doing ONE Maiden-centric tour. Di'Anno is a different story, he has pretty much been living in 1980-81 for quite a while now (with a few exceptions). But Blaze is essentially taking a break from promoting his own career (I believe he just finished an acoustic tour before starting this with Di'Anno) to celebrate TXF and VXI (which, by the way, are great albums that I don't see regarded by the actual Iron Maiden to have even existed).