I would 1st (of course) take a look at what's already out there, and done in Arch-land, as a point of reference.

Find out what many users desire, (ex: search social media / forums for popular questions. Not only app-wise, but configuration, features.

I'm just guessing here - really depends what you hope to achieve out of your project.

Most users outside the hardcore Archians, will opt for Arch based, easy guided usage / install.

Maybe you want something more easy to work with - or you could keep closer to traditional Arch, and enhance that?

If security is the idea, usability can take some balance. Kicksecure project for Debian serves as a nice example of usable / hardened, if security is one of your goals (might not be the goal if seeking new to Linux users).

Ask yourself what kind of users are you trying to attract out there. Anything from a distro you always wanted to see on a distro, that you felt partly missing?..

That is where I would start.