I would also like to add the idea of a set rank because i hate entering a new campaign and i have to start from private again. So what im suggesting is when i beat a battle or campaign i earn seperate xp to my steam account(and/or in-game account) and as i win more battles i rank up outside my campaign files. so when i start a new campaign i wont have to start as private because i earned xp from previous campaigns i fought. This wont carry over however to online unless you want it to. But the xp gained from finished campaigns/battle should vary based on difficulty. Do you guys get what i mean?

You can edit your rank in, "C:\Users\<name>\AppData\Roaming\Running with rifles\savegames". Just open up the save file and open the "<random numbers>.person" file. Locate the, "authority="0.000000"" bit and change the 0.000000 to anything between that and 1.00000, which is max rank. The job_points is also your RP, change that if you like. This is cheating, so I still recommend that you rank your way up.