Simple test anyone can do - do a 18 mph to 0 stop using only the front wheel. Measure the distance. Now, get on your bike with a holder (like a velodrome start) and accelerate from a standstill over that same distance. Note your speed as you go by the other end of your stop. Your max braking vs your max pedaling force for the rear wheel will be the ratio of 18 mph to your speed from a standstill.
For example, say it takes you 15 feet to stop. And on your hardest start you are going 6 mph at that 15' point. Your deceleration stopping force will be 18/6 = 3 times your starting acceleration force.
So, are you comfortable with an animal of a rider fully 3 times as strong as you stomping on your rear wheel built just like your proposed front wheel? Would you trust your body and bike to a front wheel stomped like that? If yes, go for it. (I wouldn't.)
Ben