IMO bases should be very dynamic and stick to real world defensive strategies. I think the design team should really do their homework on how defensive structures are created and what type of thought patterns go into creating a defensibly position. I think that it should be very rewarding for players to defend positions and continue to monitor areas that could be attacked (like constant garrisons for the hardcore gamer). I also think that attackers should be actively trying to scout defensive structures to estimate a garrisons strength and how the defenses are laid out. I also think that there should be all types of defensive structures from trenches to fortresses. The designers though should definitely take real world ques from past and present wars.