what is the alternative to face id?

I'd have thought that it would be less than optimal to use the phone that way (even if it does turn out to be possible, which I'm fairly sure that there will be at least a close approximation to your description)

(IT security expert hat on) You really should consider protecting your smartphone and other technology with passcodes. There unfortunately great value in getting access to peoples information, particularly passwords and online accounts (all of which are wide open if you do not have your device locked).

Setting a password on iPhone also enables hardware based encryption of the phone's storage, a massive plus point for the Apple platform.

Passcodes are to say the least inconvenient. People hate them and often choose stupidly weak passcodes. (the number of times I've stood on the London underground and watches a fellow passenger enter '1111' or '111111' is immense...) TouchID and FaceID are great technologies that take the edge off of that. Indeed I use TouchID with raise to wake and find it amazingly smooth experience. Apart from entering my passcode when switching the phone on first thing in the morning, I'd not even realise there is one.

I'd urge you to reconsider adoption of FaceID, or switch your order for an '8plus and use Passcode/TouchID instead.

(lecture over 🙂 )

You do not have to use Face ID, or a passcode, however it will limit some of the features of the device. You will not be able to use Apple Pay, and a few other functions. It also leaves your data available for thieves to access if the phone is compromised by theft or loss. Up to you.