Looking to move multi vendor site to web app HTML integration

I recently posted a project which was incorrectly described, updated description below...

We are looking to move our current multi vendor site to become a HTML web app integrated onto the vendors own website, meaning as well as the vendors shop being on our website, we would like to be able to easily integrate a stripped down version of their shop (Ideally 8 ''featured items'') from the vendors shop onto their website.
By doing this we hope to allow customers to purchase items from the shop on our website via this HTML integrated on their website as well - this can be via the payment page opening on our website, if that makes sense?

As well as this we are looking to update our current multi vendor system, we currently have over 100 vendors on the website however the pages are not created dynamically, we would like to be able to generate vendor pages dynamically based on the page information we input.
We currently use WCFM.

We are also looking to find a way to ''feature'' certain items above the shop so they stand out above the other items.

Finally we would like to change the design of our homepage and shop layout, we have the design ideas for this just need them implementing.

Finally we