Map Custom Authentication Pages to a Custom Post Type

I am building a Bricks Blueprint Site and want to have a Custom Post Type for Account pages (Custom Authentication Pages) as it is a group of select pages that should be together I think.

I have read the doc from Bricks (LINK) but when I try to add the CPT post/page for login alternative in Bricks, it does not show up. Apearantly only pages can be selected.

I found one other topic, no answer on it yet (25 june).

Can anybody help me with this please. Is there another option to make this possible?
Thanks in advance.

Really nobody with an idea?