I would asume that for busy places Gatwick LHR MAN its nevr going to hapen because of the scale of operations and the ground movements - look at the capacity at LHR and how it falls when LVPs in operation.
There's a school of thought that Remote Tower might actually be possible at major airports - systemised, high volume operations, where the tower view is important but the Controllers have other ATM systems available, such as SMR and/ or MLAT.