^ Yup. The case height with 54mm cooler support would come down to ~70mm + 2 x material thickness. Given that you don't intend to support high-TDP components, I would get rid of the side fan, perforate both sides, the top (duh) and the bottom.
Beside the SSD on top of the brick, the height of the case would allow (with a little concession) to install SSD's on the side panels but I don't know if that's something you'd like to pursue.
A last idea I have is to ship with a full-cover top bracket that enables installing the SSD (which appears to be floating now

) as well as a 120/92mm top fan. This way, no matter the heatsink, one can use any 120/92mm fan on top (plus the added few mm's between the top panel and the fan would help reduce the turbulence noise)...