Stock Allocation - Orders "Locking Down" available stock

We have a issue where an order's stock allocation "Locks Down" available stock so that we cannot ship out other orders. 

for eg. we have 100 units of Item X on hand

Customer 1 orders 300 and will wait 4 weeks for production

Customer 2 orders 50 units but we are unable to ship on the system owing to Customer 1's order "Locking Down" what we have physically on hand.

The option of "rolling back" Customer 1's order to Draft stage or Not Allocating the stock so its freed up for Customer 2 is a risky (this removes the re-order and allocated figures from the system) and tedious especially when there are many orders for a single product.

PLEASE HELP!!