I do similar except I have one on teslas, one on splash damage, one on air D and one on single shot. This way my base is still at least as strong or stronger than a max TH7 even when upgrading 4 defensive structures and I'm not exposed for days with having more than one splash out of commission.
No real reason to commit a builder to collectors. You make sooo much more raiding than you do from collectors it's not worth the builder. Save those collector upgrades for times of poverty...

