I think that <space/> ought to be moved from transcr to core in order to be more generally available (e.g. to TEI Tite). It doesn't make a lot of sense for <gap/> to be there but <space/> not to be. The two elements have clearly distinct purposes: <gap/> is for recording "a point where material has been omitted in a transcription", whereas <space/> "indicates the location of a significant [intentional] space in the copy text".
This phenomenon is hugely widespread in the transcription of legal and legislative documents. Take a look at the attached document to George Washington (also at http://lister.ei.virginia.edu/~drs2n/space-doc.jpg\) . There is no reasonable TEI element to use between "bearer" and "Horseley" other than <space/>.