Indeed I think it will be even better that the wizard detect automatically the POS from the IP of the user.
On the POS definition we could set two IPs (usually one IPv4 and one IPv6 which should be unique) and so the wizard does not ask for the POS but set it automatically depending of the request IP.

Instead of using a wizard, I'm wondering if it will not be better to have a simple list of all point (accessible to the user) and have a tree_open action to open the sales window from that point.
But we will still need a menu entry for all the POS Sales for the sale administrator to check that all sales are done at the end of the day.

The same applies to cash sessions which should be opened from a sale point.

I'm not sure it should be managed the same way because user may change frequently of sale point but the preferences are not designed for frequent change.
Instead I'm wondering if it will not be better to ask for the sale point when opening the "POS Sales" menu entry and then if a point is selected, restrict the field value with a domain constraint (and no constraint if not point is selected).

In order to ease the introduction of sale points it will be great if the user can set on it's preferences the current point which is working on.

This is similar to issue8396 but for sale_point module.