These research questions regarding the resurrection never take a step back to a more fundamental issue; did Jesus actually exist? I'm sure most would reply absolutely yes, but only because we've been conditioned to think it, and asking the question may sow seeds of doubt.
I don't know if there was a real Jesus, but there's a lot of perfectly valid academic opinion that supports the mythical position. Without doubt, the evidence either way is actually weak. By asking this question it inevitably leads to a dawning realisation that talk of the resurrection of a person whose existence can't be verified is absurd.
Actually they are not 'radical' and nor are they fringe. I'm not sufficiently well informed to be able to form an opinion, and nor I'd suspect are you, but the fact is that Jesus as myth is an academically sound position. Even if it's wrong, it's based on such a dearth of evidence that it renders detailed stories of Jesus essentially inconceivable.
Mythicism -- the proposition that the Jesus of Nazareth depicted in the gospels does not represent any actual person -- is well-established and has been argued since the late 1700's. Its proponents have primarily consisted of academics, mostly theologians or philologists and even a few clergy. The arguments of mythicist thought are firmly grounded in exegetical principles, are carefully argued with scholarly precision and nuance, and offer compelling solutions to otherwise intractable problems with the NT.
Despite the internet-based notoriety of an handful of unlettered, amateur hacks, mythicist research today continues to be conducted by bona fide scholars relying on a vast wealth of material ranging from apocrypha and patristic writings to the Nag Hammadi and Dead Sea Scrolls, not to mention archeological finds.