Membership app and editing Role access - best way for new site?

Hi

I've been using Perch for a company intranet for the last couple of years, which is now going to be completely redesigned and rebuilt, so I wanted to make sure I will be using the CMS the best way possible, so welcome advice, best options, ideas to make it easy for users.

On the existing site I've used htaccess username and passwords to restrict section access for relevant staff, however, so that they only have to remember one password on the new site, I envisage using the Membership app, giving specific access to certain sections/pages.

Currently, the staff have three levels of site access by htaccess on folders relevant to them. The client wants to use just three usernames and passwords for all staff depending on their access level, so they only have to sign in once. It just makes it easier for them to maintain users in this very simple way as there is a high turnover of staff after the summer season finishes, when they only have to change three passwords:

1. Part-time Staff - single username and password for all - restricted access to general site and their department information pages.
2. Permanent Staff - single username and password for all - gives access to general site as above, plus their own specific permanent staff info pages.
3. Managers - single username and password for all - gives access to all site pages.

ROLES: On the admin side, apart from the main administrators, there needs to be section/page editing by nominated staff, eg. Catering Manager has editing rights to only catering section pages; a Retail Manager only has editing rights for retail section, and a Operations Manager has editing rights to only Operations section.

And, there will be a blog used only for news not comment, as well.

So, if I've managed to explain correctly in all my rambling, I'm wondering if using the Membership app (for those 'three' users), together with setting up Role per User for certain pages/sections and, finally, having a blog/news app together is the best use of Perch for this project?

Would this be the best way of using Perch for my needs? Advice gratefully received!

Many thanks!