How long should it take?

[stevesh]

There's no practical way to answer such a detailed question here in the forums (though someone might try), in part because we don't necessarily know what you are referring to in each instance. For example, I don't know what 'carriage paid' means (free shipping?), nor 'price segmentation' or 'average cost pricing'. In what sense should it be 'barcode and ISBN compatible'?

Almost every thing you list can be done in Zencart, but some may require custom programming.

If by 24 hour support, you mean Zencart support, you're looking at it. Server choice is up to you.

My suggestion would be to install Zencart on a test server (including the sample products) and fiddle with it for a while, then come back and ask more specific questions, which we should be able to answer.

[gilby]

Personally, you are thinking of taking on a massive project with absolutely NO zen-cart experience
There are many here with years of zen-cart experience that would think twice before quoting on those specs.
I also am unsure what some of your terminology means?

I suspect it will require lots of custom coding (open ended quote)

html and css are fine....
but ecommerce and zen-cart require LOTS of php and mysql coding experience.
To be blunt, I doubt you can deliver this project at this time.

You will need to install zen-cart and "play" with it a lot before quoting on such a job.
Time for you to develop this? (Years.... imo)