As per the thread: https://groups.google.com/forum/#!topic/foreman-users/Wf4vRM8byCg

It seems some users have needs where their DHCP proxy auto IP suggestion isn't necessary and confuses them.

I suggest making an option (checkbox) in each subnet, "auto suggest IPs", with a help text "if enabled IPs will be suggested for hosts in this subnet" and letting people make their choice. If there is no DHCP proxy available for the subnet in question, we default to 'false'.

On the Host form, we should only display "suggest new" if the subnet has the "auto suggest IPs" option enabled.