Your fastest open-cycle resource usage is water. If you can recycle your water, you've got much slower mass-growth per unit of time in free flight. This could make the difference between 8 hour spacewalk capabilities and 8 day spacewalks.
You're not thinking creatively enough. When life support fails and astronauts have to live in their suits for extended periods of time, what is the difference between an extended spacewalk and having to live in your suit for a while?
The other is the catastrophic failure, like a major hull breach. In that case, space stations, bases, and submarines are all designed in modules. You cut off the damaged area and move on with repair. If you happen to be in that damaged area, you're dead. These suits are massive, difficult to get into or out of (requiring multiple people), and also require extensive prep/charging/loading to use. As they become more complex, this all just becomes even more true. In this catastrophic failure scenario, the astronaut would be unconscious in seconds and dead shortly thereafter. It's not like you can just hop into a suit, and heck - even if you could you again would not need to be in it for days.
The other more general issue is that you're adding complexity to try (and probably fail) to solve extremely obscure problems. So the net result is an increased chance of running into an issue. We want to be going the other direction unless there's a very good reason not to. Of course avoiding single point of failures is one of those "very good reasons" but I don't see any single point of failure that this would eliminate.