Yes the Rack Pack is an interesting option although I doubt I'd ever need that and front panniers.
Point of using the Trunk Bag was its ability to function as a rear mounted handlebar bag - fill it with all the frequent access stuff and, since it is small and easily removed, carry it into cafes and shops.
One of my fancy ideas that never quite works in practice. In the end I just strapped a camping mattress and groundsheet to the top rails of the logo. Volume similar to the Trunk Bag and saved the 800g weight of the bag.
