I am very anti-brick/block, but very pro poured concrete.
In my opinion, traditionally placed brick and/or block is akin to a chain. And as we all know, a chain is only as strong as its weakest link, which in my opinion, would be the mortar.
That said...I am not all that familiar with how strong a block wall can get if you filled the cavities up with concrete...considering that the cavities are always going to be offset by ... I guess...at least 50%....which I am guessing could limit how big of an aggregate you can actually have in the mix.
A smaller aggregate would allow the wet concrete to flow in and around the cavities better and fill them more completely.
But does a smaller aggregate lead to weaker concrete?
Now, this is just me...kinda thinking out loud here...but with the weight of a vault door slamming shut and when the door is swung 90 degrees to the wall will the weight of it levering itself out away from a block will....over time, will the wall withstand that kind of "abuse"?
I can just picture cracks in the wall or the mortar'ed joints spreading outward from the vault door's frame.
The other thing to keep in mind is that just because your basement floor is concrete it might not be thick enough to withstand the weight of a concrete block wall on top of it.
I have been in homes before where the "sub-grade" under the basement slab wasn't all that smooth or level, so in some places you could have 3 inches of concrete or you could just have one inch.
If you put enough block on a floor so thin, I am thinking it is going to start cracking.