I'm in the same boat (SDI and PADI instructor), and I think you could do this correctly, without making them do the e-learning etc. by conducting an SDI class in CW, then making a global referral from your SDI-self to your PADI-self and conducting a PADI OW session. Then you can legitimately issue a PADI OW certification, and by receiving the referral back from your PADI-self, issue a SDI certification. Your only additional cost would be the PIC.
Your best answer is going to come from PADI, but I think based on what I know of the standards, what I've outlined above is within both agencies' standards. If I was going to do it, I'd call both to make sure I was playing by the rules.
I'm pretty up-front with my students about why I think SDI is better for them than PADI, and I haven't had one yet who came looking for a PADI card. I have had a couple of refugees from other shops who wanted to finish their PADI Divemaster with me though, that's more to do with the other shops pushing people away.