Random response created because I misread you
First of all, I think the combination of resources and confidence can make building a lot more interesting. In Tremulous build points were really a threshold of how many buildings you can have on the map. You would usually use most of the BP inside your main base and spend a few on an aggressive forward (other playing styles were highly efficient in scrims but I seldomly observed them in public games).
Now you have a greater motivation to spread your base over the map. Building a forward will give you the tactical advantage (healing, ammunition, combat support), generate a significant amount of confidence (75% of a buildings confidence value, 100% if it's close to the enemy base) and let you generate more BP that you can use to rebuid/enhance your main base and generate even more confidence.
On the other hand, you would still want to keep all your forwards under control as they can easily boost your enemy on a higher stage if left undefended.
So effective building could mean that you try to balance these opposing goals based on your teams level of coordination and preference. I hope that will lead to more diversity in strategies!
Actual response
I'd keep it simple for now. Destroying a well placed / important building could earn you more confidence but I fear this will make the system rather intransparent. If we award good building as such we would open our system to some forms of cheating, such as intentionally hurting oneself and hopping on the medistation or mindlessly kamikaze-poisioning your enemy to boost your booster. That being sad I'm sure that if we introduce a measurement of the quality of a structure, we would find it handy at some point anyway.
