For myself, it would be really helpful if I could move the primary usergroup with promotions. Software such as Subdreamer tends to only take into account someone's primary usergroup, so if I wanted to promote someone to to a group where they say, no longer saw advertisements (not a purchased upgrade, just a sign of good will for activity) I would not be able to do so because Subdreamer only recognizes the primary usergroup, which I can't automatically change.
Ex:
I have my regular registered group. In (insert software) I can set the "registered" group to determine permissions for users in the primary group "registered" in Xenforo. This group in in the CMS software is set to see advertisements. The CMS software only recognizes primary usergroup. I have another group in both the software and Xenforo called "promoted" that someone gets put into after x number of posts, years registered, etc. I can promote them into the group as a secondary group currently, taking away advertisements within the forum, but I can not automatically have them moved into a primary group, meaning the CMS software is unable to see something changed-therefore the user still sees advertisements in the main website.
Second Ex:
Say for example you checked "Deny" for deleting posts/threads for the general registered group. You absolutely don't want anyone on that scheme being able to delete posts/threads. You decide, "OK, if they register with an email associated with my company, I want them to be able to delete their own posts/threads after they are active for a bit." So, I make a promotion to "Company" for everyone that has an @mycompany.com email, and they are added to the secondary group (their primary is not changed). I make a promotion that will add each user to another secondary group, "promoted", members are added to when they reach 50 posts and 90 days registered that has "allow" listed for deleting own threads/posts. OK, so everyone who did not register with a company email will be placed in the group, get a larger avatar size or something, but they won't be able to delete their own content because "Deny" was checked in their base group permissions. However, the folks who registered with my company were only added to the company group as a secondary group, so the base "Registered" group Deny for deletion still applies to them, and there is no way to automatically move them out of the primary group (or any secondary for that matter).
For this same reason, I suggest that primary group change option be added to user upgrades as well. Just my two cents
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