Massive Type Errors on tRPC 10 Legacy Router against MergeRouter

We're trying to upgrade to tRPC 10 but I am running into a massive type clash when trying to merge routers. Our tRPC 9 router is huge. I've interop'd all of these routers and the legacy router itself, but when I get to the point at which I am merging my new router with my old legacy router, my .merge statements on my legacy router blow up a massive illegible typescript error. Attached is a glimpse, can provide more info if necessary