In the UK, if one forgets (thankfully) about BAe, the only company with design and construction capability is Bombardier.
When Bombardier bought Shorts in 1989 they made absolutely sure that all overall design, assembly, flight test and marketing skills dispensed with - apparently in response to Canadian union/political pressures to ensure that there would be no threat to these capabilities held by DHC and Canadair (as they then were). Shorts became a (very successful) sub-assembly designer and manufacturer but getting back into the overall design, manufacture and assembly of something as sophisticated as a fifth / sixth generation fighter would be an exceptionally tall order.