I’ve only seen a couple episodes of Doctor Who so I can’t really give a fully informed answer, but I also can’t imagine anything could sway me from joining the Legends. Hell, staying behind on the most dangerous missions would be even better. Much less chance of death/injury, I could help run ops on the Waverider and still enjoy all the cool tech on the ship while interacting w/ my amazing team. Sounds like a perfect setup
Well… The Tardis does have a near-infinite number of rooms including the Zero Room that helps heal beings, including a recently regenerated Fifth Doctor in “Castrovalva”. No to mention the Tardis is a living being who is protective of her passengers as expressed in “The Doctor’s Wife” and will help you if you have a Terminal Illness but it’s not your time to go yet. The full extent of the healing properties of the Tardis haven’t been explored yet but I can safely venture that it’s infinite. Hell, we stil don’t know the full extent of what a Tardis can and can’t do, period!
The Waverider is a bit limited. It couldn’t keep Martin Stein from dying, or Nate Heywood from dying without Ray’s serum intervention, nor can it reconstitute itself like the Tardis can after a while.