Quid,
Two points, I suggest, to consider.
(a) does one not consider the case of RLW + planned burn to constitute one of the TOW limits to be considered for a particular sector ? The approach and landing WAT limits are part of the RLW calculations. FAR 121.195(a) seems to say just that sort of thing. I can only take the view that your philosophy might be a little adventuresome. A chap in your position might find it wise to take competent legal advice on his interpretation of the rules, I should think.
(b) the WAT limits have nothing at all to do with obstacles. They are airworthiness limits and only seek to provide a modest climb capability regardless of any other considerations. If there be obstacles then they are considered separately and usually cause a reduction in weight to suit the required obstacle clearance.
Regardless, the AFM imposes the WAT limits as TC limits. The pilot abuses such limits in other than emergency situations at his/her legal risk.