The current slice-based regressors provided to afnI_proc.py are already seen as regressors - they are not manipulated, except for possibly removing some time points from the start of each run. Therefore, if you could insert additional regressors to make a larger file (more regressors per slice), the updated file could be fed without any changes to afni_proc.py at all. At least, I believe that to be the case.
Peter is currently working RetroTS.py, and might be interested in this operation. Are you going to convolve as in: for each time point, put down a basis function scaled by the unconvolved RVT? Which basis function do you plan to use, GAM? BLOCK(1)?
Thanks,
- rick