Doing a low j.D makes you vulnerable when you land, so you would never want to do that.
and for confirmation 6P does not combo into j.D
-didn't see you mention FRC air dash in. Since they will most likely be blocking low during your string your j.D will whiff, although should they happen to stand up I still don't think this is an effective way to keep pressure on, if you want to have iad pressure just 5p 6HS iad etc. If you want to use tension to keep more pressure on I'd just end with tatami FRC for run up bait / 2k / youzansen or dust / throw. Although it might be useful on someone like pot (I'm not sure if you can j.D right off the ground on him while he's ducking.. it for sure won't work on anyone else) incase you can catch him low guarding after the j.D and ad j.S j.HS 6HS etc... it just doesn't seem very practical to me
and as I mentioned earlier j.D will leave you vulnerable after a whiff with no FRC, so you leave yourself wide open or use tension for nothing