I think that the expensive-cache idea will lead to more aggressive/play harassment to shut down people that are trying to hoard resources too early.
Please note my concern about Penals being able to punish cache building much easier than other factions - later in games commandos with their demos will provide a quick hit and run on these expensive caches. The concept is good though - much more decision making about where/when to build caches in team games with a distinct penalty to your fighting ability when doing so early and haevier blow when they are destroyed