The crucial factor in the size and shape of the Shuttle orbiter was the requirement that it be able to accommodate the largest planned commercial and military satellites, and have over 1,000 mile cross-range recovery range to meet the requirement for classified USAF missions for a once-around abort from a launch to a polar orbit. The militarily specified 1,085 nmi (2,009 km; 1,249 mi) cross range requirement was one of the primary reasons for the Shuttle's large wings, compared to modern commercial designs with very minimal control surfaces and glide capability.
I heard some opinions that the wings could be diminished if the requirement of 2000 km cross-range was not forced. So weight and complexity of Orbiter could be reduced.
But less wings would lead to higher landing speed of Space Shuttle. It already had landing speed about 340 km/h, much more than conventional aircraft.
Could Space Shuttle's wings be diminished?
My personal guess they could not..
The question suppose all the rest requirements of actual Space Shuttle are not changed (payload mass, payload bay size, etc).