Sounds like all the bases are covered, MDF is good for prototyping, ease of working and Im the fist to grab whats waiting round rather than lashing out on more materials. Alloy angle is a good one for this type of runner too, I find the more complex and domestic ones tend to pull out or fall apart and as you say they take up space. F/Glass sounds like a great idea, as long as someone does the work-smelly sticky stuff- and can have some of the similar attributes of MDF depending on the use and mechanical loads.
Long term test will tell!