A constant hertz (cycles per second) detuning feature would be very handy for SWAM strings when used in an ensemble.
This would solve a problem when using the current constant cents master tuning to detune multiple instruments in an ensemble. For example, a detuning of 15 cents can sound very good in the lower register of an instrument, but in the high register it will sound too extreme.
On the hand, a constant Hertz detuning of, for example 2 Hertz, will give a gentle beating of 2 cycles per second, no matter what register the instrument is playing in.
Other synthesizers, notable Kurzweil, have implemented constant Hertz detuning, and I know form experience that it works very well.