if you remove the brake arm, the sprocket will lock up and spin your cranks forward. unless you want to pedal 30+mph, it's not a good idea.
i've heard of people removing the brake guts, but i've never tried it. i've seen how-tos on youtube, but never paid much attention. i think you have to modify/make some spacer or something to get it to roll properly.
i suggest getting spending a coupla bucks extra and get a freewheel.
or, look for a vintage "un brake" on ebay. they made them in the eighties to convert a coaster for freestyle bikes.