I'm afraid we're mixing concerns, I didn't ask to allow both
transactional and non-transactional operations on the same cache, I
understand there are good reasons to not support that.

What I need is control for batching, i.e. be able to send a set of
writes on different keys at one specific point in time, combined with
the capability to avoid repeatable reads in the same cache: definitely
there are many ways to emulate a similar behaviour, I could collect
all writes in a map and then send async operations and block on them
all, or open transactions for the span of single operations when I
don't need to batch.
Consider as well that I might be pushing a thousand of packages of
10MB each, I'm not of the idea that keeping these in a distributed
transaction log is healthy for performance since I don't need rollback
capabilities, being this already handled by Lucene.