I have allowed a similar homebrew feat in one of my games that instead of requiring the target to be flanked by 2 of your allies worked when the square/hex that your line of sight to the target passes through before hitting the target would have been flanking them had you been standing there instead.
Mainly, the reason was because parties I tend to DM don't have a lot of smashy fighters who go in an flank. Usually there is a Rogue and a Fighter doing that with a divine caster and an arcanist hiding in the back. As such, there are no 2 people to flank.