They would have done like in MTW where you were able to play all the campaigns from the same menu. Or like in RTW where with the Barbarian invasion addon, the original game could be modified to use the expansion same features. Here instead it seems that you can't use the FOC abilities in EAW. They have been real stupid to divide the two things.
Ok. Do you have already some xml from the mod you want to make or starting from zero? If zero I will modify some for you.If you have already done something, rar all, upload somewhere and give me the link to work on. (I recommend rapidshare)
Yes it's essential for most things. The most disappointing thing is that the original campaigns are not playable in FOC so no addition on FOC can be used in the original campaigns. :-\