The sponsorship scandal has taught us a lot of lessons. You can establish a lot of rules, but when someone is determined to circumvent them, there's no way of ensuring that everything is done within the spirit and meaning of the act.
Even if all the members of an executive of an electoral district were prepared to endorse the necessary loan or line of credit, they wouldn't be able to do it if they were required to comply with the limits permitted in the context of an election campaign. If the limit were applied to individuals, that would require such a large number of endorsers that it would become impracticable.
I don't believe that this solution is viable in ensuring that all candidates have the financial resources necessary to conduct an election campaign on an equal footing.