This should be a very simple fix, and many of the other inventory management companies use it b/c we need it.
It gives the option to pick which sku's you want to sync on which channels.
Having the pressure to sync 1000's of products on multi-channels is very unrealistic, risky, and dangerous. Twice, I have overrided and screwed up my entire inventory having to spend days re-counting and getting straightened out. Both times I was very angry.
Shippingeasy is one of the best companies I work with. This simple, missing feature is really holding back your entire inventory program b/c there is no control. Inventory is really complicated on our end for reasons beyond our control. Some of the channels are extremely complicated for inventory "for example Ebay". Trying to roll the dice that everything will be right and then pushing the "big red override button" and closing your eyes is shortsighted.
It has been a nightmare. I know it would be very easy for the developers to fix and would be a great business/financial boon for shippingeasy inventory program.