Allow ability to consume driver memory on worker hosts not master (option for clustermode to wait for returncode?)

My scenario is this:
EC2 master (488GB RAM of memory and 64 cores)
Autoscaling group of up to 8 EC2 workers that get registered with the master

I send 100s of parallel spark-submits to the ec2 master but I seem to be artificially limited to approx 240 in parallel (if driver of each spark-submit takes 2gb memory). I would like to know the returncode of each sparksubmit so deploymode is client. I understand using deploymode of cluster would not wait for the returncode.
Sparksubmits are not submitted directly to worker nodes as EC2s are ephemeral beasts that pop-up/down regularly, while the master can simply redirect tasks to another worker whenever another worker is lost.

This new feature would allow as many spark-submits in parallel as there is total memory in the pool of 8 worker nodes (ie don't limit by memory of the master) AND make each sparksubmit wait for return code.