So I am putting final touches on my current build, and I searched high and low at no avail for a perfect case for the modern building. I am using a Revodrive for my drive, and I don't believe any machine needs internal optical drives any longer and everyone should buy one usb Blu-Ray or DVD drive that they can then share among all their computers. I ended up using the Antec SOLO II due to the simple nature of the box which leads to the best spacial usage available.
All that to say, I was wondering if anyone knew of a case that was thick as the SOLO II that did not have any 5.25 or 3.5 bays as they are useless to SSD users, and make cases unnecessarily large meaning more airflow is needed to achieve a healthy static pressure, and maybe have a single 2.5" mounting spot on the bottom or top of the case thus making the case 5 inches shallower...
Another relatively related thought is to put the same level of hooding on the back as we use on the front with the extra space to achieve silence, and inset the PSU the way we used to on old servers so the noise is further removed from audible range....
While i do agree to some point on your argument on 5.25 slots not being as useful... it still has uses more than just optical drives, like Fan Controllers, Water reservoirs, installing multiple hdds on 2 or 3 5.25 slots, even for suspending hdds, etc. I do agree that less are needed, and probably most can live without, but would be too expensive to cave into both market segments, so less is fine like solo II has 2 and the R4 also same two.
Now if you are looking for something with high airflow that doesn't have any hdd cages or opticals blocking the ideal line of airflow to your motherboard and its components, then look into the upcoming Corsair Cambridge 540
, it has a separate chamber for PSU and 2.5 hdds, while still has the 2x 5.25 slots it doesnt block the layout of it as its on the back side. The case is very open, and was design for great air cooling, but im not sure how it will behave on the noise department. Personally im still deciding to order one atm and just try with quiet fans like antec 140s and a HR02 macho, and for storage just twin 840pros and single 2.5 7k1000 1tb (both paced on the hdd cage on the back of the mobo. But i still have my doubts as the case is too open both front, top , extra chamber. etc.
Since you like smaller, you could also look into Bitfinix Prodigy
, it does have 1x 5.25 hdd that its removable, it has hdd cages but they are removable also, and its kinda small case its mini itx, but its design to fit a lot of hardware inside. You can even remove all the hdd cages and use the side pannel 2.5 mounts for ssds and 2.5 laptop mechanical drives... not sure how quiet is the case, but just throwing some ideas for what you are perusing.