Suggestions needed for bringing saps back to M2TW

I would like to bring back saps from RTW to my mod of M2TW...

This might be done easily with text changes and adding RTW CAS models of the little sap tent/shed back for sieges...

BUT, the problem I have run into is that there does not seem to be a place for saps in the campaign game initial seige setup screen or in the custom battles setup window. I would have to remove one of the other three seige methods (not using artillery...) ladder, ram and tower, which I would not like to do.

Any suggestions would be welcome, or if someone has already done this for another modification, please let me know.

What I would like to do in the end is have a sap go to its end like in RTW (with the underground digging), and then have graphics setup so that the sappers detonate explosives underground... so not just only would the wall come down after they were down, but maybe have a small explosion or something...(this might not be possible...) but that is another problem to be tackled later...

Thanks for input,

AT