When you are in the Dark Sanctuary or the thieves guild I feel your bounty should go down faster than it does in the open world. My better half expanded on my idea by saying that when housing comes along it is another place that should speed up the rate at which your bounty decreases.
Apologies if someone else has already had a similar idea, typing this seemed to be easier than doing a search.
Guild Leader of
The Twelve Knights, AD PVE, PVP and Trading Guild on the EU Mega Server
"That which does not kill us makes us stronger"