will be building/will have built...

(a) uses the future progressive tense and describes an ongoing action (building the tuckshop) that will take place in the future.

(b) uses the future perfect tense, which describes an action (building of the tuckshop) that will occur in the future before some other action or event (the end of the year). Thus the focus of attention is upon completion by some target or milestone date. I would prefer (b).

Peripherally, on the question of native speakers, I'm a native speaker ad I haven't the faintest idea what a tuckshop is, or why you'd want to build one.
The choice of alternatives depends on what you want to express, and what you are currently doing:
a) means you haven't yet started building, you will start before the end of the year, and you may or may not finish it before the end of the year
b) means you may or may not be building it now, but you will have finished building it by the end of the year.
c) and d) aren't correct as they stand, and would have to be modified:
We are building a larger tuckshop now and will have finished it by the end of the year.
We have been building a larger tuckshop, and will finish it etc.........(or they work if you just leave out "the end of the year" phrase).

So what the hell is a tuckshop?

Oh, all right, I googled it and now I know. It's mostly UK and Commonwealth countries, and for some reason Arizona.

we will complete
we will provide
we will build

It doesn't have to be more complicated than that.

Thanks to all of you for your help.

Sire, that is utter nonsense. Life creates myriad situations and language, through the use of different grammatical structures, illustrates those differences.

No it's not.

"You're like a sheep's head, you know - nearly all jaw" "Look here, if you kick me again I'll - Yaroooh!" "Talk about Pontius Pilate fiddling while Carthage was burning..."

http://www15.brinkster.com/hiamie/greyfriars/greyfriars.htm

Both MJ and C illustrated/have illustrated [just one small example] that you are mistaken, McTag.