Moving systems to a different Satellite Capsule

Hi!

I have about 4000 hosts on four Satellite 6.3.5 Puppet3.8 Capsules.
One capsule is dedicated for dev-hosts, one for test-hosts, one for qass-hosts, and one for prod-hosts. Each capsule also works as a Puppet CA for that env (which I regret as using Satellite as a CA would have been better in a migration situation like this).
We want to upgrade to Puppet4 to prepare for Satellite 6.4.

I have added four new 6.3.5 Puppet4 capsules and want to move my 4000 hosts to those four capsules. This seems harder than I first thought.
I added new capsules to avoid problems by upgrading the current capsules to Puppet4, it is safer to move hosts over slowly to a new capsule. That way I can test and adjust Puppet manifests to work correctly with Puppet4 for all host profiles. I have created additional Puppet environments where I correct diffs between Puppet3 and4 and can gradually move hosts to the new envs.

I have been thinking of a few of options for how I can migrate hosts to new capsules:
- bootstrap.py (/var/www/html/pub/bootstrap.py on sat6 and capsules).
- A custom ansible-playbook first gathering all relevant info about a host, unregister, clean puppet certs, re-register on new capsule, adding info.
- Changing parameters on the hosts and satellite to switch them to the new capsule.

I need to make sure that the following information is not lost when a host is moved to the new capsule.
- subscriptions (a few hosts has additional subscriptions added)
- parameters
- correct content-view
- correct repos enabled on the hosts

I have found bits and pieces with some info about such a migration, but not enough to be confident that I do this correctly.
For instance this presentation has one slide about migr:
https://www.redhat.com/files/summit/session-assets/2018/S1031-10-things-you-didnt-know-about-Red-Hat-Satellite-6-Distribution.pdf

Have anyone performed a migration like this and can share experiences?

Best regards,

Erling