The turnstile idea was nothing more than a tea bar discussion in the Aerial Delivery Section at A&AEE. Although every time crossover came up we would look at each other and say "We should have built the turnstile".
Staggering the paradoors doesn't need to be as severe as one at the front, one at the back such as the Horsa, the C-46 and the Hastings had exits staggered by only a few frames and crossover was less of a problem, mind you the lower drop speeds also helped.