[dingaling]

The only security feature I really want is a preinstalled user-configurable firewall.

Keeps your system firewalled and your apps sandboxed and there's less of a need for constant OS patches.

But it's notable that even 'privacy first' Apple doesn't ship a firewall because that would interfere with the market for ad-supported apps.

[javagram]

Configuring a firewall sounds like the opposite of the ease of use Apple wants to be associated with the App Store. Doubt that will ever be preinstalled.

I believe you could theoretically install one on iOS using the VPN functionality available... a quick google only finds “guardian mobile firewall” which is still in beta though.