The cost of swaps has a minor role in the demand for swaps. The demand for swaps is driven almost solely by the price movement of bitcoins, it is not dependent on the swap cost.
Looking at my experience of about 1.5 years lending money at Bitfinex I have to agree here: Many (most?) traders don't really seem to care if they pay 0.1% a day or 0.9995% a day or 0.15% a day in swap if the prices move several % anyways.
Since nobody seems to have noticed it, I have suggested an alternative flexible rate that would be similar to going long on BTC while lending out USD: have a low % fixed rate while the trader's position is negative and a high % profit share (+ probably the standard FRR+x% on unused funds, to prevent abuse). This means someone who is unlucky in trading only pays e.g. 0.01% swap, but if the prices go up, they pay e.g. 20% of their earnings to the swap provider (both numbers are up to the swap market of course). People offering funds under these conditions would be betting quite hard on the market going up, but might choose not to trade themselves for example because they don't want to deal with closing positions or the risk of down swings.
Interest would be checked hourly(?) and debited/credited daily from traders to lenders, as it is done currently.
Just out of interest btw.:
Let's say there are 2 hours of 1% FRR, 20 hours of 10% FRR and then again 2 hours of 1% FRR --> how exactly is the amount due at the end of the day for FRR calculated? The FRR at a certain time of the day, an average over the FRR the whole day (sampled at which intervals?) or something else?
I did comment on this earlier. My concern would be that the lender is getting the lowest rate when the swap is most vulnerable (the trader is losing). Of course if swaps are as risk free as Bitfinex purports them to be, I would not have any philosophical issue with this.