Disney looking for a new writer and cutting the episode count suggests to me that they don't like how much the current script is going to cost and want to find someone who can either trim it down or write a whole new, more reasonably priced script. That makes it seem to me like they're putting cost ahead of quality. Cost is important, but Disney is so wealthy and Disney+ is so fledgling that maybe they should follow Netflix's lead and worry more about quality, trusting that quality will lead to subscriptions.
Besides, if they really want to be so concerned with cost, they should consider that four episodes released a week apart means that people can subscribe, watch the whole run and cancel before the month is up. Six episodes, on the other hand, would require staying subscribed for an extra month, which would be a lot of extra revenue to help offset those two extra episodes.