I cannot think of any that come to mind quickly. I really want to see mixed-form factor cases also. My sense is you could get a 3.5" to 2x 2.5" converter.
On the slim DVD also, that may be asking for a bit since you would need two side-by-side 3.5" bays and I am guessing three 2.5" bays below and a slim DVD above the 2.5" drives. Best option is probably using converters for the 2.5" drives then getting away with IPMI 2.0 for the BMC's remote image mounting if possible.
Patrick, thanks. There are a number of 4 x 3.5" hot swap with slim dvd. My problem with using 2x2.5" in a single 3.5" is that the bays are hot swap with backplane so i don't know how i can get 2 sata connections in the same bay