I understand your point entirely - I think and would hope that the majority of my colleagues are well aware that most of our standing agreements and intermediate en-route level restrictions are far from the preferred profile of most aircraft. Unfortunately these are the rules we have to play by, reducing overall complexity by removing certain traffic types from a sector and thus increasing overall capacity.
LBA in particular is very restrictive inbound, you are effectively forced to follow the same profile that manchester and even liverpool inbounds have to follow. It also has the frustrating effect (for you I suspect) that you have probably found yourself speed restricted against such liverpool/manch traffic, so that we can get you through the same point ( 10dme Monty @ 200) at the same level!!
A good point you make about MAAS, a given rate does imply a descend NOW. I was quite surprised when I discovered quite a major technique that I hadn't been taught. There's probably a reason for it to which i'm not privy!! MAAS may have kit to help them decide - I don't know to be honest - although I imagine it would be possible to do simply mentally (what do I need you at in 5 mins, etc, etc, calculate rate).
WW