DDS15 — How to address different history requirements for live data and historical data?

We have some customers that have different history requirements for live data and for historical (i.e. TRANSIENT_LOCAL) data:

• For live data flows, they don't want to miss any sample (i.e. KEEP_ALL).
• For historical data for late joiners they don't want to align the entire history, but only the most recent subset (e.g. KEEP_LAST with depth=1).

In the current spec, it is not clear how to facilitate both requirements in the same Writer. Some vendors have added proprietary features (new QosPolicy attributes or new Writer properties), but it would be nice if the DDS spec would offer a formal way of facilitating this, one that is portable between different vendors.