Disable the conditions and go through the process on frontend on the users behalf then re-enable the conditions after the basket is created. I don't know what else to advise as there is no backend basket creation process at this time and even when that's added it'll probably still respect the upgrade/registration conditioning.

You need to click the offline payment gateway button when going through frontend then click the confirm link on the payment slip page. You have to do everything the user would normally have to do.

This works as follows and always has worked as follows. It is the ONLY means to create a basket on the users behalf.

1. Login as Administrator on Frontend
2. Visit the users profile
3. Click to Upgrade them to whatever plan you want
4. Click the offline payment gateway button
5. Click the confirmation link on the payment slip page
6. Login as Administrator on Backend
7. Go to CBSubs > Baskets
8. Pay the basket

If you can not see the plan in step 3 then neither can the user as you have either access permissions or conditions preventing them from seeing it. Turn off the conditions so the user has access to the plan then continue through the steps. Once you're done paying the basket adjust the conditions again or ensure the conditions make sense from an upgrade standpoint.