I am running into a few issues with --specified-id. First off, it would be nice if --specified-id could be set in the dfx.json for an individual canister, so that the command line option would not be necessary.
Also I’m running into an issue where if I use --specified-id for some canisters, but then try to simply deploy another canister without --specified-id, I am getting the error Canister be2us-64aaa-aaaaa-qaabq-cai is already installed.
It seems like dfx is not appropriately finding new canister ids if the id is already taken by another canister.