Hi Chuck,
This looks to be a great idea. I see now that you can get ER collet blocks which I have been thinking about but as I only have R8 collets at the moment I may have a go at this myself as I have a big chunk of hex brass too. I know I will be limited to bar that I have a collet for (unlike ER collets which have a range) but for most of what I do I have standardised on my stock sizes.
Matt