For completeness, here's my theoretical analysis to augment our empirical observation that users don't mind fine-grained mode being removed.
Fine-grained mode provides two benefits:
Executors are brought up lazily
2) Relinquishing cores
Cores are relinquished back to Mesos as Spark tasks terminate
Fine-grained mdoe does not provide the following benefits, though some think it does:
a) Relinquishing memory
The JVM doesn't relinquish memory, so it would be unsafe for us to resize the cgroup
b) Relinquishing executors
As for alternatives to the benefits, 1) is provided by dynamic allocation, though we need a better recommended setup for this as I document here: http://apache-spark-developers-list.1001551.n3.nabble.com/HDFS-as-Shuffle-Service-td17340.html
There is no alternative to 2), but we've generally found that the executor-level granularity of dynamic allocation is sufficient for most.