If the infrastructure supports it, for the duration of the disruption, in the future, is it possible to operate the railway there as two single lines, bringing passenger services to the same side as the transfer to coaches, and keeping the other line for other movements? ....
Not really - neither line through Trowbridge is signalled for bi-directional use so trains cannot reverse at the platform (I have known it done once, "in extremis").
With signalling changes, it would be possible to reverse trains from Bath at the northbound platform, but not at the southbound platform unless they ran "wrong line" all the way to Bathampton. And again with signalling changes it would be possible to reverse trains from Chippenham at either platform.
Logic during the current stoppage (I am seated in my armchair telling the people on the ground) with appropriate signalling would have been to reverse Bristol and beyond trains at the Northbound Platform twice an hour, and Swindon trains at the Southbound platform every 2 hours, with once in every 2 hours the train from Bristol extending to Weymouth and arriving into Trowbridge from Weymouth. The Weymouth services could pass each other at Pen Mill ... shortish layover as usual in Weymouth, and the Bristol to Trowbridge service that extends to Weymouth (so can't be used to form the next Bristol service) conveniently being replaced by the service that arrives from Weymouth into Trowbridge at about that time. Without the need for 2 trains an hour to reverse on the WoE main line is they can reverse in the platform at
TRO» , the reversals on that main line should be manageable.