Late to the party here. 
For those asking to drop the AIO support. Why? It's a by-product of the 2-slot VGA support, can't see what having support for AIOs hinders in any way. Unless you want to put a 3.5" HDD in there which is, nowadays, useless and rarer than using an AIO in the Sentry?
I hop on the 2.5-slot VGA support request bandwagon. The space is already there, I believe in you, you can make it happen!
As for the possibility to access the back of the motherboard, have you considered a magnetic cover? I don't know how magnets so close to the back of the motherboard would interfere which electric signals, but it could be an elegant way to address the closing mechanism (as in there's no mechanism).
I haven't really looked into this space-wise but could it be possible to move the front USBs from the bottom (considering a vertical positioning) of the case to the centre, below the power button? I think it would be more eye and symmetry pleasing?
Speaking of which, going on a mass production, why not let the buyer select either a Type-C (with the newer connector) or a Type-A (with the old, blue bulky connector) hub, much like it is possible to choose between different color coating? Btw, can more colors be added to the choise?
(Hoping a standard-compliant one emerge before mass production) PCIe 4.0 riser, please! I know VGAs are nowhere near the 3.0 bandwidth limit atm but, with the rising of both PCIe 4.0 VGAs and motherboards, it will happen more and more frequently that a build won't POST simply because the end user forgot to switch PCIe slot speed from "automatic", or "4.0", to "3.0", meaning the build must be taken apart and either a PCIe 3.0 (or lower) VGA has to be used to enter BIOS or PCIe 4.0 VGA has to be mounted directly to the motherboard. Either or which is not really feasable nor user friendly.
