Sure you can, its your beer.
I would ferment in primary as one batch for 2-3 weeks. Then bottle the first 7L. Split remaining beer into 2 secondaries. Add coarse ground coffee beans in dry hop mesh bag to 7L for 2-3 hours (0.5 - 0.8 oz of beans should be enough). Gently swirl the beer up and taste every hour or two to make sure you don't go overboard.
Add your cocoa addition to the other (I have no experience here on how or what to add).
Primary #1:Spruced Winter Warmer #2: Empty
Secondary #1:Berry Rhubarb Wine #2: Empty
Kegged: Cascadian Dark Ale
Bottles: Surly Bender clone, Big 50 Barleywine, Framboise Lambic, Dark Belgian Strong, Kicked by a Moose Scotch Ale, Russian Imperial Stout, Sparkling Elderflower Wine, Barolo Wine, On Deck: Orange Pale Ale, 2H IPA