I know they'd have that reaction because every time I've seen that fanart posted to "medium sized " audiences on Facebook, Instagram or reddit it gets laughed at, rejected, say it doesn't look scary, it looks ridiculous, like a bumblebee, feminine etc.
Because of how controversial the casting already is, Pattinson needs a suit that blows people's minds and make them say "That's Batman". You can make something new with the design without it receiving a ton of backlash like it'd with that one that was posted. Ive seen other cowl fanarts that get a far more positive reaction and even have changed people's opinions on Pattinson a bit. The cowl is one of the most important parts of the costume, it's Batman's face and this is not the time to do weird experiments. He needs something recognizable.