While we shouldn't judge by today's standards I don't think it is unreasonable to judge by the standards set in the early stages of the French Revolution. An electorate based on a moderate property qualification only (and age and sex, of course) and free choice of candidates doesn't seem too much to expect.
The electoral system in Britain was the result of historical evolution and its inadequacies were being challenged; though the system led to an automatic bias in favour of property-owning, upper-class candidates there wasn't any official pre-selection and there were always some awkward, even Radical, members elected.
The other feature that would have been considered essential, even by British standards, was that the elected members should have a genuine right to hold the government to account and to refuse assent to taxation.
The 'model' Westphalian constitution fell a long way short of the standards of the time and the level of popular representation it included had clearly been watered-down to make it almost useless.