Magento 2 - displaying iframe in admin config panel

I want users who download and install my extension from the marketplace to go through the registration / input stream. Since a normal file system.xml

only supports static pages and does all of this using front-end models, it's too complicated, I'm wondering if I can show everything in an iframe instead?

Displaying everything in an iframe gives me many advantages such as

Design flexibility. Magento buttons / elements are ugly. Ability to use the same iframe my other ecommerce suggestions Much less engineering time as our team is much more comfortable JavaScript / CSS than PHP / XML etc. So my question is how to implement the iframe and are there any disadvantages that I am missing?

I see it is possible for Magento 1