Okay, can Dragon be depressurized and then repressurized back? Somehow I think it will require a lot of additions to its construction, and also alternative hatch instead of docking module (was already done with transparent dome for Inspiration4 mission.
SpaceX have announced an EVA suit, so they do apparently have plans to support such missions.
This article states that the entire capsule would be depressurised and repressurised, as there's no integrated airlock. It also specifically mentions the prospect of servicing Hubble (though with no details).
That strikes me as both the most basic approach and a capability which would be useful for other reasons as well. Another option might be to carry along an airlock, perhaps stowed in Dragon's trunk, and mounted during flight, though that itself might require an initial (full-capsule-depressurisation) EVA.
