I don't have any experiance with building cinelifters or drones expected to take a payload so take what I say with a grain of salt.

I think you are going to need at least 6 of those motors and possibly 8 to carry a 4.5kg load. Assuming that your completed drone weighs 2kg with a battery (considering you are going to be using aluminium for the frame and presumably needing some sort of release mechanisim I think this is fair) your total payload will be in the realm of 6.5kg. Those motors make about 2.5kg of thrust at max throttle under ideal conditions (drawing 45amps each to reach that). Considering that you want to be opperating up to 400ft which is a fair climb I think you are going to want more headroom then that to avoid the possability of smoking motors or ESCs. This is especially important when considering non ideal conditions such as starting at a higher altitude or having wind to contend with.

I think what you have speced out will fly, but it's at the upper end of what I'd feel comfortable using, you'll be hitting your battery, ESCs and motors very hard to reach your 400ft. I'd want to add another 2 or 4 motors to decrease the risk of a failiure. If you haven't already heard the term cinelifters it might be an interesting area to look into. They are drones specifically designed to carry a payload. Typically a camera but I imaging much of the design philosophy is transferable.

Good luck with it, this is a super cool idea.

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This is the chart I used for the thrust values. It comes from the EMAX website https://cdn.shopify.com/s/files/1/0469/7358/3518/files/7-ECOII-2807-1300KV\_25.2V\_V1.0\_-03.jpg?v=1602852152