Hey @aldub,
you’re right, we don’t offer that right out of the box currently.
I explained the general approach in a different thread here with regards to assets: Migrating values between locales
As said there the migration function can be async (as transformEntryForLocale):
module.exports = async function (migration) { ... }
For the space ID and access token you’d use something like yargs to parse them out of the process.argv. If you’re using an env var for the access token you could read it from process.env.CONTENTFUL_MANAGEMENT_ACCESS_TOKEN
Maybe that’s already enough for you to start? If you want a more detailed explanation I’m happy to help you out there 