It sounds like the best option is to create a new comic (as in, uploading it to a new "comic"). Do as you've said, rename the old one to just... Old?
You can also notify your followers through a post, or make a page where you explain the resons (if you want to) and link to the new comic.
Edit: You mention the old comic is still ongoing, I probably would stop updating it at some point, where it feels good enough to stop.
You don't have to merge it, unless you want to yourself. Making several comics are tedious and time consuming (10/10, would not recommend if you have a life, if not, go ahead! 8D)
So if I were in your position, I'd probably just create a new series, upload the new comic, keep the old one and rename it to old, notify the readers and update it until it feels good enough to stop.
I've restarted one of my comics like 5 times, but they were also less than 30 pages.
The reason always was that I didn't think it was interesting enough to draw and kinda quit halway through.
I never did pubslish them on any sites tho, for the reasons above xD
However, I'm currently putting all those into a PDF adn offer them to my patreons, because... Well, why should I not show it? Even tho I put a lot of hours into the comics, I feel like I can't post them online as they're incomplete, contains spoilers and overall looks goofy xD