Call, Meet, Lunch - not useful but how to change?

[Simumaz]

In activities, there are only 3 options and these are not helpful. Call is OK, because that is a usual sales activity. Meet is OK, again because it is a usual sales activity.

Lunch is not usual - in our case, would never happen. What would be useful is to be able to replace lunch with Email - which is what we would do if we were not calling or meeting. However it's not easy to see in the code how to change this and in which files it needs to be changed (I have found it in a few of the files but realise it will break things unless I change them all).

Thanks