Apply assembly constraints to 2 parts of a cable or pipe flexible sub-assembly

There is currently no good way to assemble one grease tube assembly or lead strap assembly into multiple parent assemblies.  Say I want part number 123 to be an assembly of two grease fittings on either side of a tube.  123 can be used in multiple assemblies, all with inlet and outlet holes in differing locations.  It would be nice to be able to assemble fitting 1 to one hole with two coincident constraints (cylindrical barrel and surfaces) then use similar constraints on the other fitting to a different hole.  The tubing/cable in-between would flex accordingly