An ASA 500 with an ASA 1m F/1.8 that has a 135mm corrected field, large enough to take the FLI Kepler 6060
All in all it likely hits around the $2M mark
For a more realistic approach it would be a 12" F/3.6 that comes in under 20kg to use with an ASI6200. It would be the largest instrument that I would feel comfortable using on my ASA DDM60 and allows everything to remain portable.