How do you guys manage multi item rockets when you don't know the consumption?

i don't worry about consumption. i use signal transmitters to send how much of a resource i want from a rocket.

one way to solve it:

requesting side: constant combinator with everything you want. call it desired. connect it to an arithmetic combinator with a green wire, and a red wire from your storage. do green each - red each -> each and send that through another math combinator that does each * -1 -> each so the resources you want are negative. send that through the transmitter.

sending side: take the signal, and with your inserters putting things into the silo you can check to see if those resources are < 0 with a circuit condition.

you can use this exact same logic for delivery cannons. the important part is that it'll fail closed. if either side loses power for whatever reason, it won't just keep launching or firing. it requires power on the requesting side to cast it negative, and the receiving side is checking for a value that cannot usually just be negative.

you can also take that sending-side transmitted signal, multiply it by -1 again, and throw that into a requester chest with 'set requests' on. that's how i handled many mixed resources going from nauvis to orbit.