Until catenary is extended south of Washington to at least some destinations in Virginia, there is no real application for a dual-mode locomotive beyond what is already available (P32's in Empire Service). Now if a decision is taken to replace NER trains with MU's to complement the new Acelas, dual-modes make perfect sense and there are off-the-shelf models from several manufacturers that can switch power sources seamlessly. If locomotive-hauled coaches remain the choice, dual-mode engines were aptly described as "expensive toys".
Amtrak wants dual-powered equipment because they want to reduce station dwell times in busy terminals--such as Washington D.C--and so that passengers will always have access to lighting, etc.
Are you saying that Amtrak should consider EMUs that travel with diesel locomotives?