Actualy on google there are some mods to replace the 16 maps with the bigger ones :/
On my disc version I found a mod that basically let you download all the 64x version for the original BF2 and also changed the AI folder as necessary to let you choose how many bots you could play w/.
Unfortunately, when I bought the steam version, I deleted the disc content. I doubt it would be too much hassle to find the mod download again (actually, it's the Battlefield 2 64 Player mod, I believe it's called) but I wanted to know if someone had done all the maps.