I feel the real problem here is mixing and matching kubernetes with ECS. They aren’t really meant to play together and were never designed to integrate together.
If you add Karpenter (https://karpenter.sh) to the cluster it can scale based on the rules set out in the configuration and sends out requests directly to the underlying cloud orchestrator. Which in practice means it spins up new compute resources near instantly.
I see that they added support for Azure aswell recently (been a while since I used it)