From a UI perspective... just adding some sequencer parameters as mod destinations is sufficient for User Interface and workflow. If they are mod destinations, we can target them via envelopes, lfos, mod wheel, slider, mod matrix, etc. They don't really need to have any extra UI/menu implementation.
A single mod destination for these parameters, that would offset the value of all steps... a "global offset" for all steps.
1. Mod Destination: Sequence Velocity Offset - take the mod destination value and apply it to all steps velocity amount.
2. Mod Destination: Sequence Duration Offset - take the mod destination value and apply it to all steps... ie: +50 DC value to Sequence Duration would increase the duration by 50% for all steps. -30 would decrease the duration of all steps by 30%.
3. Mod Destination: Sequence Ratcheting Offset - Divide Mod Input by 16, and add that much to the ratcheting value for all steps (up to upper/lower limits: 1-8). ie: +50 value to the mod destination would add 3 ratchets to all steps.
4. Mod Destination: Sequence Note On/Off (probability) - If value to mod destination value is <=64 all notes are on / as set in the sequencer.. >=65 all notes are forced off. Then a random SH LFO synced to 1/16 steps and targeting the NoteOnOff offset with +127 value could trigger probability 50% on, 50% off... and further modulation to that destination could customize the probability (force off) range.
5. Mod Destination: Sequence Last Step Offset - Divide input value by 8 and add/subtract that many steps from the current last step setting. (constrained to the lower/upper limits 1:16) ie: -50 DC value to last step offset would subtract 6 steps form the current "last step" set for the sequencer. If it was set to 16, it would become 16-6= 10 Then you could route mod wheel or other source to it to get crazy poly rhythms or quickly swing the sequence to play only the first four steps, two steps or single step in repeat.
Adding as these as Mod Destinations would be an elegant solution and not require any UI development... just wiring up the destination values to offset all sequence step values. Would allow for so many interesting behaviors with the sequencer, controlling from mod wheel, slider, lfos, envelopes, etc..