"Currently, the DAP-2695 is NOT supported. The hardware is supported by OpenWrt, but there is no profile for it yet. Additionally, the boot loader looks for a custom header in the firmware image, like the DAP-2553 . "
I don't know if it is the same firmware header format... you'd have to look at one of their stock firmwares... but I did figure out the DAP-2590 firmware header, which simply needed an extra bit set from the wrgg format.
My working tree includes a patch to mkwrggimg to allow editing that field, if so. But, it's not the same CPU as the 2590 so the rest of the tree probably won't be too useful.
I'd recommend comparing the top of the firmware with that of a DAP-2590 and see if the format looks similar, then if so, use mkwrggimg.c as a reference to look for any fields that have different values.
Also I expect a few of the D-LINK idiosyncrasies probably hold across the DAP series, like the emergency web server working best with the reset button held down all the way through the process and the way to bust into a shell from the stock firmware cli.