I would move the batching logic into Process Flow. For this, set the queue's Send to Port to "Do Not Release Items", so you can later manually release the items.
The Batch activity allows to set a maximum idle timer, meaning if no new token/item is added to the batch within the given timeframe, the partial batch can be released. The released token then sets the target quantity on the combiner and releases the items.
This is obviously not foolproof, as any kind of delay on the upstream processes would mean a partial batch is released despite items of the same type still being present. If this does end up being a problem, you could implement a counter that keeps track of how many items of a given type are still in the system (have not passed the separator yet). Only if that counter reaches 0 would the idle timer in the Batch activity become active (by writing a corresponding condition to the "Start Criteria" field).
modelo-60x40-PF-batching.fsm
