doctor had wanted to switch me from my Apriso to Imuran. To me that just seems like a huge step to take.
What makes that seem like a huge step to you? There's risks also to having long term, untreated inflammation and ignoring it. Your UC could spread in extent or severity when undertreated, resulting in a severe flareup in time. Long-term inflammation increases your risk of Colorectal Cancer. As untreated inflammation can turn into dysplasia (a precancer), and then into colorectal cancer. So, I'd say it is safer to treat inflammation with a medication like Imuran than to not.
Good luck on the scope, let is know how it goes. Unless your symptoms have changed dramatically, I would not expect a much different verdict than the least time.