I have thought about the same modification.  Still in the building process so no decision made yet.  I did find the following photos of another builders open deck on a NE Dory.  Here is the link:

https://www.flickr.com/photos/blue_heron_rva/with/8552471635/

I came close to doing this also. I dropped the idea due to cost. I ran up against the old budget wall!

   I too would like storage and am considering this modification.  It appears it would also to make stepping the mast easier as one would not have to lift it above the thwart. drawback I see to enclosing is that water that travels down the mast would drain into the locker.

   bearnkr here is how you solve that problem.  Recess the forward bulkhead of the compartment.

   Here is another idea.  Instead of a cut out in the compartment deck, you attach a collar to the bulkhead of the compartment. 

   Here is how the second option looks completed.  Of all the options this is the one I am leaning towards.  The forward hatch provides additional buoyancy and storage, makes access to the bow for boarding easier than stepping over the mast partner that spans the NE Dory in the plans and if one had to quickly remove the mast for any emergency there is no need to lift it above the mast partner [not sure if that is the correct term] simply un-lash it and lift a few inches out of the mast step and it is free.