A response to your post indicates that the amount isn't that large, which suggests that if there is even modest support for the ideas -- especially among even middle-income people -- it shouldn't be that hard to raise.

Sure, there'll probably be some elections in which the deposit is lost. If the approach to government is even a little bit important to more than a tiny handful of people, it doesn't seem like that should be a significant barrier.

I mean, really, I can't believe that the risk of a couple weeks wages for a single person per constituency is a substantial barrier to finding candidates who hold a view that is held as important for even a modestly substantial part of the electorate.

Historically, people who hold political views strongly have been willing to risk a lot more than that for them.