@late-author-46106, welcome to the community!
Based on what you described, Flyte is a good fit. As you might have already noticed, Flyte also has support for running tasks on AWS batch. Leaning on the declarative power provided by the sdk, from a client's perpsective, kicking off tasks on aws batch
looks very simple. You'll need to configure Flyte to know about your
aws account, but that shouldn't be too hard.
You mentioned that when pipelines are not running you don't need compute, but you'll have to keep in mind that Flyte's components (esp. the control plane and the data plane) will consume some resources, not a lot. Here's a
component architecture diagram.