Hi wamphyri,
I think its possible to just change the availability dates / renown costs in the sim files on each type of sub to allow for different flak gun set-ups, i'm going from memory on what i think i changed on SH4 but i believe its the same on SH5. hope that helps.
not sure you can alter single mission equipment as the missions are set with a date / time frame so only kit available at that time would be on the uboats.
