1. Flash stock, open camera, test that it works.
2. Use your favorite file browser with root access (Samsung MyFiles or whatitsname doesn't work) and go to to /data/cfw
3. Find .bin file there, that's your C
are, copy it to a safe location.
4. Flash favorite 4.3 mod with favorite 4.3 custom kernel with SE permessive. (Agni or Boeffla, or use stock, but be aware that certain themes make WiFi not work)
5. Open camera, confirm it doesn't work.
6. Copy .bin file into /data/cfw, re-open camera.
I know you tested SlimISP files, but this method works ALWAYS for me, at least on AMCHA 5.x and TGP
Also, the alternative is to flash custom rom with stock kernel. Open camera to generate SlimISP bin. Flash custom kernel
HTC Kaiser . CM6 ......... OC@530mHz - Kitchen Watch with NTP .
HTC Leo .... CMX OC@1.19gHz, Jellybean
HTC Ace .... CMX OC@1.5gHz, ICS + Sense 4.0