I’m so glad to hear that!! This implementation has been putting in work, as Nomad executes cross-chain proposals with it regularly (most commonly to deploy & enroll a new chain).
I totally agree it would be very nice to have an event indexers could pick up that indicates initiating cross-chain call execution 
Do you think that event should be emitted once for each destination chain, or once with a bundle of every destination chain? Personally, I’d say once per destination. Perhaps a higher-level Proposal event could include a bundle.
As a side note, I’d propose exploring some more general naming:
event CrossChainCall(uint32 destination, bytes32 callHash, Call[] calls);