Fortnite data mining is still going strong, as FNLeak dug out what seem to be assets for a new LTM, dubbed Seize and posted them on Twitter. The new mode apparently resembles capture the flag format in shooter games, but is still WIP.
Proof regarding Capture the Flag mode in Fortnite is still tangential, as the data mining only revealed a folder branded Seize, containing another one called SeizePack, which in turn contained a file named "Flag".
Therefore, all the discussion about a possible Capture the Flag mode should be taken with a grain of salt, as the mode could prove to be a long way from release due to the "Flag" item being in an early stage of development. Another possibility is that the mode will never actually surface, as FNLeak also warned that the playlist might not come out at all.
Should this mode come to pass, it would probably be the first instance of an extreme Capture the Flag where two teams of 50 duke it out. Games that featured such a mode earlier either had movement abilities tied to characters or other ways of moving faster, but something along those lines in Fortnite be priceless, as it would be a hard life for anyone to attempt stealing a flag with 50 people on their tail.
It is hard to imagine such a mode in Fortnite, even harder still as a fun one. Chances are high it would simply turn into a zerg versus zerg fight. With that in mind, other, smaller objectives could potentially be added across the map in order to dissipate the blobs of players.
While making a fun version of Capture the Flag in Fortnite's clusterlove would be hard, if anyone can pull it off, it would be Epic Games. They did produce some of the best Capture the Flag experiences in gaming's history through Unreal Tournament series.
It was a long time ago though, in an era where not everything was battle royale and not every arena shooter needed to incorporate unique character abilities.