I come from Plesk. Plesk has some amazing commands but the software can feel bloated which is why I like aaPanel. That said, a couple things I can say that definitely are some must-haves if you want this panel to really stand out:
1) Add aaPanel commands to SSH. For example, in Plesk, I can do "plesk login" and it will generate a unique URL for me to access the admin control panel. This is such a nice feature. This would really help a lot.
2) Add Support fro Imunify360 and Bitninja. They are great products and used in the enterprise world vastly. If you want to truly be used by businesses and such, you need this support
3) Add subscription services and support for resellers and integrate with WHMCS. Webhosts would use this panel if this support was there.
4) An absolutely needed accessory is a plugin or integration with a truly exchange based email. Something with a nice web panel such as Roundcube Plus without the premium cost. Having the ability to support CalDav and ActiveSync are a must. Plesk has this but as a premium addon. Where it falls short is truly allowing for the publishing and sharing of calendars. Add this and you'll see this panel vastly used by serious hosting companies. Businesses live by Exchange/ActiveSync email, shared contacts, distribution lists, etc.