I think a simple addition to PlayFabMultiplayerManager:
An override of SendDataMessage(...) that accepts a PARTY_SEND_MESSAGE_OPTIONS argument -- to have a bit more control over the sendOptions.
Right now the various SendDataMessage methods all accept a DeliveryOption -- which can only be "BestEffort" or "Guaranteed". After passing the DeliveryOption through SendOptionsFromDeliveryOption(...) we are given a PARTY_SEND_MESSAGE_OPTIONS that has sequential-delivery and opportunistic-coalescing turned on. This isn't always desired.
(Also, separately, it would be nice if SendDataMessageToAllPlayers(...) allowed any control at all over the sendOptions)