Only the debugger can play upacked maps. But as you know you can't realy run the debugger in fullscreen nor can you go online with it. But you can use the debugger to do edit maps on the fly and reload the map to see the changes (instead of exiting the game and repacking the RFA).
Once you get the map to what you want you can repack it.
The debugger loads unpacked stuff beginning at the games root, NOT the mod's root folder! So for example level RFAs are loaded from mods/bf1942/your_mod/archives/bf1942/levels
while unpacked levels are for use in debugger are loaded from here:
bf1942/levels
.