Honestly, you said he has about 10K followers, if a lot of those are his routine customers I’d say post a poll or several and take the customer feed back. If majority are on board it might help convince him to move more online. As far as storage just look into rentable storage spaces if thats all it will be used for, likely a lot cheaper than a proper shop rental. I do want to point out though that you should double check and make sure none of the distributors he gets from have any rules about not selling online, I had a store once where certain distributors would only let us sell brick and mortar. There can be work arounds to that but just be careful. Hope this helps.
Highly recommend writing down ideas and thoughts as they come along. If you’re like me and have tons of ideas but then get distracted by either everyday life events or even secondary ideas coming in you’ll lose those original nuggets that very well could’ve become something grand. Plus having all those thoughts side by side is a great way to gather inspiration for even more ideas.