Talking from experience to remove the dependency if you don't want to start a new mission from scratch:
Make sure you set it so ArmA stores your mission.sqm in the old readable fashion.
Go into the editor with a new faction in your mod line (and with Leights/RHS still loaded, obviously) and delete all references to Leights in the modules and any objects of Leights that were manually placed. Save.
Exit the game and go into the mission.sqm file. Search "LOP" with ctrl+F and "LOP_" as well and delete any lines which refer to Leight's pack.
Go back into the launcher and then remove Leights from the mod line. Try opening your mission. If it loads, you've successfully removed the dependency. If it doesn't, add Leights back to the mod line and start back from step 1.
Do the same with RHS if you don't need the mod any more.
I did this a few months back and don't regret it for a second.