Basically you can scale to what ever size you want. I mostly brew 40L. But you need to keep a bit of head space in the fermenter to allow for the krausen (foam) that the yeast makes during fermentation. If your pushing the limits of your fementer space, folks use fermcap-s (brewing product) or Simeticone ( various brand names, over the counter medicine for baby's with gas) to reduce the foaming.

Also If your talking about just adding malt extract and hops to your fermenter, its not that simple. Malt yes but what you get from hops depends on timing. Huge amounts of dry (fermenter) hops add great flavors and aromas to IPAs, APAs etc but contribute very little bitterness. You will want bitterness to balance out the added volume and extra malt and for that hops need to be boiled in a reasonable quantity of wort for something like an hour.