Phase 1 of these feature is in 1602 production
270 votesMatt Piechota commented
I came here to make the same suggestion, so I gave it 3 votes.
I would love to be able to deploy an application to multiple collections, or in the reverse, select a collection and pick multiple deployments to it. The only way to do it now is to create a collection that has other collections as part of it - and I would prefer not to go that route so if something breaks, it's easier to diagnose where.