You might be able to implement this using an external count timer mapped to midi reassignments of the rough and fine delay settings and depth range.
It would be a huge amount of calculations based on a variety of bases for interpolation, and quite complicated by use of the depth knob which seems capable of doubling delay times on it’s own, and even then you would be limited to 1/128th of the fine delay range.
The Rose does not appear to have a splice in/out function it it’s internal architecture, operating instead by means of rescaling the clock and scan rate of the entire buffer, thus it seems unlikely to me that we will see this an upcoming update. I could be wrong, it may do both. – In which case yes, I would love to see this feature too. It would make Frippertronics much easier, especially if accompanying existing music.