This article describes the collaboration of Space Systems/Loral with Constellation Services International (CSI) on a COTS proposal for ISS resupply : Space Systems/Loral Proposes Bus for NASA's Cargo Needs - Space News/space.com.

The CSI proposal to the first COTS funding round involved using the Russian Progress vehicle as a space tug to bring a CSI designed cargo spacecraft up to the ISS for docking and later to remove it for de-orbiting. (See this presentation at CSI for details.) Although it was probably the closest to an off-the-shelf system of any of the COTS proposals, it was rejected. This was probably due to the heavy reliance on Russian hardware and also because it did not advance US rocket development (see this article by Charles Miller of CSI about their COTS experience.)

The new proposal replaces the Progress with a space tug derived from Loral's big 1300-series satellite bus. The spacecraft would be stripped down to basically just the propulsion and guidance systems and then a docking adapter would be added. Just as Loral's satellites can be launched on wide range of rockets, so could this system.

This new approach obviously helps to get around the objection to the foreign hardware. Also, the development of a space tug would be a whole new addition to US space capability that could benefit other applications.

I'll note that Loral had also submitted a proposal in the first COTS competition with its Aquarius water launched rocket. Loral has continued to do some development work in this area but the current proposal doesn't seem to involve Aquarius in any way.