Given that this improved in the transition from the Librem 13 to the Librem 14, you should be optimistic about this for a hypothetical Librem 16. Purism - – Librem 14
Seems fair.
I wouldn’t expect you to have to supply a password because of a change of MAC address because I think the password is being stored against the SSID.
Of course if you are filtering access in the wireless access point by MAC address (generally a bad idea anyway), this is going to be horrible. As such therefore such a change would have to be optional.
The best way of doing this is for the WiFi card to support changing the MAC address i.e. host supplies a new MAC address and the WiFi card uses it. Someone else would have to confirm whether the specific WiFi card in use supports that. If this works then this is just a software change and could come along later on, even retrofit to existing laptops.
Given that this improved in the transition from the Librem 13 to the Librem 14, you should be optimistic about this for a hypothetical Librem 16.
I think we covered that adequately at Touchpad buttons for enhanced security and ease of use and Touchpad buttons on Librem laptops?
Cool - unless the the movie was scary stuff in which case you and your friend could be freaking out by now. 
I would expect more cores in a hypothetical Librem 16. As above.
I really really wouldn’t expect either Xeon or ECC - it would do bad things for both cost and TDP / time between charges.