Suppose we allow only short published stump speeches and nothing else.

What prevents the green team from registering 200 yellow candidates who will all submit yellow-sounding platforms in order to split the vote?

Don’t we want to allow the public to judge candidates on more than their ability to write a single speech? Politics and representation is picking someone to perform tasks as our agent that go well beyond writing a single short speech with lots of lead time.

Well that doesn’t happen currently so it probably won’t happen in this scenario. Nor does it really happen in countries that have implemented bans on private campaign financing.