Hi Kevin,
Yes, through customization, portal users can preview shared QuickBooks Scheduled Reports within portal.
With regards to assigning reports, portal users cannot be assigned reports; only Method users can be assigned reports. However, as a workaround, you can assign a contact to a user and with some additional logic on the portal page, reports can be filtered accordingly.
I highly recommend performing heavy testing on portal if you intend to modify portal screens.
If you need more assistance implementing this, I can put you in touch with a paid in-house consultant or you could look into our Method Solution Providers.