The "Problem" of novelty candidates is not with the candidates being able to run, or even potentially win elections.
The only "Problem" is that, someone with a bin on their head running on the platform of "I'm not Nigel Farage", is assessed, by significant numbers of voters, as a better option than the "serious" candidates.
If you want the novelty candidates to stop mattering, You have to have "serious" candidates voters can take seriously.
Not racist literacy tests, or high registration fees