I have built the hardware and I have some questions

Hello, I have a few questions.I am building a complete computer with fpga and all other boards, and I have some questions:
1. What firmware should I choose, mesa, remora or, write my own?
2. I want a universal solution, so what input/output boards should I design?
3. Should I design my own case or choose a ready-made one?
Here is one of the prototypes:
-32 outputs 24v 0.5A, 32 inputs 24V, four boards
-4 analog servo -10V.. 10V outputs, 4 encoders input, one board
-Fpga 96 IO board with buffers, one board ()
-Firmware - ported and modified mesa for SPI interface.
-software driver - modified hm2 driver from source code.
-3d printed case.
-Computer Raspberry pi 5 aluminum case

all works fine and stable 
   

I'd either go for mesa or riocore, both types will run on a Spartan 6.

Riocore is pretty good in that it has quite a few mesa doesn't support, has also port for a number of different FGPAs. The only issue is that it needs rebuilding of the driver for each time you change to fpga config. RIO also has a Ethernet plugin that uses a w5500, as of yet no plugin for the Ethernet chip used on the Mesa boards.

Mesa is very very mature, one driver is all that is required for changes to fpga if you keep to the standard mesa set of modules. SmartSerial is a big plus as well.

I built a 7c81/7i90 clone using a spartan 6 dev board and some custom PCBs, mesa & riocore firmware both ran fine on it.

Keep up the good work.