5000 kgs / 5000' AMSL
I think your question just about comes up with one answer only, "Mission Impossible". Must assume you are talking about lifting 5000 Kg at a time into a 500 metre dirt airstrip at 5000' AMSL. Give the almost constant high temperatures in the area you allude to you are going to have a very high Density Altitude. Flew many times into PNG airfields at 5000' AMSL and higher in C130's. It can get exciting, even with 4000' of crushed coral runway at those sort of field elevations. BTW, a Caribou has a useful payload of around 4000 kgs and would be one of the few types I would even give a second glance.
Give the dream to someone else and enjoy less stressful living.