Problem:

The surface of the runway is not flat and horizontal in general on an airport.
Annex 14 is specifying tolerable slope limits.
By that, humped runways are not excluded forming a serious 3D-site.
Annex 10 is specifying tolerable DDM- or angular-error limits for ILS or MLS.
Annex 10 is specifying also minimum fieldstrength limits.
ILS-Localizer or MLS-Azimuth station are at the end of the runway.
Landing aircraft may be completely in the shadow of the hump of these systems.
Difficult situation for building restrictions in case of humped runways.
Type of Localizer antenna difficult to determine.
Height of a potentially needed pedestal under the Localizer is difficult to determine.

Observations/Measurements (ILS-LOC):

Low fieldstrength in the shadow region
High sensitivity for DDM for objects on the hump (buildings, taxiing aircraft)

Practical solution and consequences:

Wide or widest aperture antennas installed often just due to the fieldstrength requirements.
Pedestals are installed sometimes of appreciable height.
Costly and risky decisions made on a weak basis for safety purposes.
Potentially overreacting decisions are probably made in many cases.