Some way of determining where other objects are - the Mun, other craft or debris, and their orbital parameters so we can work out the rendevous/intercept/orbit phase math ourselves

MechJeb already has all this information - it's used for Transfer to now. Please expose whatever is already collected to us and tell us what units they're in; we can do the rest of the math ourselves.

Some way to select another object is of course required - a minimum would be "Mun", "Minmus", and "Kerbin". Better would also include some way of referencing other vessels and/or debris, be it typing something in, or selecting on the map screen or whatever else.