You cannot reconvert existing map but if you have a .map file then you just simple go to radiant open the map and then just Ctrl + A to select all then press Ctrl + C to copy,

Then go to Cod Waw Radiant and Ctrl + V to paste and you have your map but all the textures will be removes automaticly and made as Caulk just delete/edit what you want or add something and its like having a start.


Also:
I have tried it works but i havent tried the opposite from higher cod to lower cause i think it would work but some brushes wouldnt apear reason is the higher cod the smaller brushes it allows like cod 1,2 has minimum of brush size 1 and cod waw has 0.25 or something...

Hope it helped.!

all i did to port was set down, took the texures i needed from cod 2 or mw any work this way, changed the iwi to dds,
"DDS2IWI-IWI2DDS converter" make sure to rename the ext.
to ( .dds ) not ( .dds.out )
open asset manager and spend a few hours converting the textures to your codwaw
now just open the map right from cod2, cod mw in you waw radiant
you notice that the normal player spawns ported over with the converted texture you added as well, but most your models are pink blocks, Killer is right BTW, just click on your pink block hit n in radiant and it will say what it is
you can get a list of you codwaw xmodels and simply change the name to your corresponding waw xmodel, or with it selected, right click in radiant
] ,misc ,model,then folders path, codwaw, raw, xmodel select the model you want
when you hit enter it will make the model appear in place of the pink block, simple but time consuming
then compile, if you missed a model it will show up as a
pink and purple stripped error block in your map but it still loads and is playable for testing

and there will be errors you just need to work it through

that's the fastest and easiest way to port