Could Barry Allen (Grant Gustin) traveling back in time and preventing his Mom's murder at the hands of Reverse-Flash impact more than just The Flash? Stephen Amell says that may very well be the case, at least for Arrow.
In the comic book version of Flashpoint, Oliver Queen is an inventor and ex-military, having previously led a group of soldiers (which included Roy Harper) collectively known as the Green Arrows. Upon honorable discharge from the military, the group goes on to form Green Arrow Industries and secures several defense contracts with the US government. However, in that alternate reality, Oliver Queen steals weapons from various C-list villains and reapplies their tech for military use.
It should also be noted that in the Flashpoint reality, Green Arrow and Vixen have a daughter together, which could be another factor as to why the show enlisted her aid to defeat Damien Darhk (Neal McDonough) in season 4.