Extensive user here, so I'm writing to post some Refinements to a couple of Plugins.
1. Ultimate Branding. Recently, I noticed an update where a Maintenance Mode can be implemented. While it appears this feature is in its infancy, I wanted to suggest that future development on this feature be similar to the Seedprod Coming Soon Pro plugin. Theirs is quite robust but seems to throw php conflicts. If WPMUDEV integrated this type of Maintenance Mode (custom builder), I am sure it would 'play nicely' with other plugins.
2. Defender: While I have not used this on my Multisite network as of yet, it seems to be a fierce competitor to AIO WP Security & Firewall...however, based on reading the Documentation, there doesn't appear to be a CAPTCHA available. AIOWPSF offers a Global Captcha to lock down Login, Registration, Commenting, etc.. Recently, we tried to use the Invisible ReCaptcha to secure our Multisite, but it prevented the Super Admin from Logging into the Network Admin & Primary Site Admin; so it was scrapped. Invisible ReCaptcha would be a great feature to add to Defender if possible.