What are the needs for a Front-End CiviCRM theme? open thread

Linked to the work on the new RiverLea theme framework, and inspired by having a play with a Contribution Page CSS and realising how easy it would be to make it look similar to Google Forms, this is a wider discussion to try and get some consensus on what's useful in a Front-End theme for CiviCRM.

There's currently two front-end theme 'spaces':

• 'old Civi', ie Contributions pages, Event pages, profile forms and listings. This mostly inherits backend UI with a few changes (input boxes are a bit bigger, font-sizes a bit bigger with Greenwich)
• 'new Civi', ie anything outputted by FormBuilder/SearchKit, which brings with it Bootstrap 3, so should work better with a Bootstrap based Civi theme.

And there's three different approaches to this, as far as I can tell:

1. Have a default style for CiviCRM front-end pages that looks nice and consistent across both spaces.
2. Have a style that does the bare minimum so that it can 'inherit' as much styling as possible from the front-end CMS theme and try to integrate seamlessly, with simple fallbacks for where it doesn't/
3. Have a style that can be customised more easily than at present, to match the front-end CMS theme with a bit of direction (e.g. matching button styles / fonts / sizes / colours).

There's a fourth option that I assume to be too much work to list as viable - which is to select a vocabulary for the front-end Civi theme to match the CMS theme - Bootstrap, Foundation, UIKit, Tailwind, something custom, etc - and then Civi would automatically integrate seamlessly.. Buttons would pick up button styles, tabs would pick up tab styles, and so on. It'd be pretty dreamy, but would require FB/SK rewriting, ntm all of 'old Civi'.

There's also maybe a fifth position which is 'I've already built so much custom CSS on top of Civi's front-end CSS, don't you dare change anything in case it breaks'.

Ignoring these last two - am curious whether people prefer a Civi front-end theme that looks nice and consistent by default, or a Civi front-end theme that works hard to integrate seamlessly with the parent CMS theme.

Comments and emoji votes are very welcome! (I guess 1, 2, 3 to select a preference)