Small idea for some fairness improvement?
Currently, there's a pretty big "asymmetry of power" between a lender and a swap user: once the swap has been taken, there's nothing a lender can do. But the taker can return it anytime of his choosing. Tough to plan for re-lending funds as a lender. The intention fo lending funds for 30 days (to not have much managing to do) does not work in reality because of that. No FRR can fix that, most FRR swaps never get lent out, unless there's big swap demand increasement, like in the last days.
Also at the moment, even if returned immediately, at least the first hour of interest of a swap has to be paid.
How about charging the first 1/48th of the time period at the time of the swap taking instead of just the first hour? That would make exactly no difference for 2 day swaps. But it encourages not to use 30 days as default for swap users who dont plan to use it anywhere near that time frame anyways.
This might increase convenience.
The asymmetry is inherent to the nature of the arrangement - you promise a trader control of some funds until they choose to release them. Granting lenders any more power to recall their funds would open the potential for traders to be forced onto more expensive swaps than they'd agreed to. Unless... I guess a feature could be imagined whereby a lender asks for their swap to be closed and replaced with a new one of the same duration, with the lender agreeing to pay the difference between the rates if the new swap is more expensive.
In general though the problem you're trying to solve (that traders will take out a swap for long periods then return it sooner) isn't really a
problem - traders already pay a premium for 30 day swaps because there are fewer of them available and they normally start at higher rates than 2 day swaps. They're not necessarily going to know how long their position will be open for at the outset, but they're paying for the guarantee that the rate they pay stays stable, regardless of how long they end up needing the swap for.
It sounds like in your ideal scenario, traders would always take a swap pre-agreed for exactly the length of time they need it for, but that's not information that exists when the swap is taken, and besides... if traders changed their behaviour to only take a 30 day swap when they "mean it", you'd just see far fewer 30 day swaps being taken at all.