Ideas

It would be great to have the option to configure aliases that map to subscription IDs.

For example, you could run this once:
> litium-cloud subscription alias add --subscription XYZXYZ --alias name

Then you could simply use:
> litium-cloud apply --subscription name --env test -f app.yaml

which would be the same as:
> litium-cloud apply --subscription XYZXYZ --env test -f app.yaml

Nice to have: aliases are shared with everyone who has access to the subscription.
But it that case it would be also good to have some safeguards in place to prevent misuse - such as assigning another customer's ID as an alias.