Ben is correct. The current scheduled date is used for scheduled items, which is a tickler feature. When we do add calendar integration it will likely not (solely) use this date for determining what to display on a calendar.
Interesting, but I see a few problems. I've run a lot of projects over the years and rarely are all my actions "due" at the same time as my project is "due".
You actually want to complete your tasks as soon as possible and I'm worried that if we arbitrarily assigned due dates to tasks and sub-projects we would be fostering a false sense of security.
For example, three weeks out from your projects due date it could look like all is well because all 20 of your tasks aren't due for 3 weeks. Then boom, the week your project is due, you realize you still have 20 tasks to complete.
Also, by not assigning any dates, you are forced to review each task and decide if it really needs a due date. Or if it can be done at any time. This is the more natural way to plan with GTD. Taking the time to review each task is a good thing!
I think you can do this today. Just create a portion of your outline "Horizons of Focus" or "Goals". Under that outline you can create all your 50k ,30k, 40k items. Maybe do this in each area, or create a new area just for this purpose.
Then you can keep anything you want in each Horizon. Notes, long term projects, etc.
I know of one person who has his whole outline created in this fashion, all the way down to the 10k project and runway level. That's one of the powerful things about GTDNext, is that you have unlimited number of levels, but the next actions can be viewed separately to still allow for fast access to your runway to do items.
I changed the title to be more accurate.
This is something we will do for sure, but we aren't to the planning stage on it yet, so I haven't marked it as planned. Thanks!