Using bi-directional logic level shifter for SWD.
Why can't you go with bidirectional logic level converter ic. For Open drain or pushpull application you can go with Texas TXS010X series leval translator and for normal level translation TXB010X can be used.

These leval translator has internal pull up resistor inbuilt as indicated below on page-3 of TXB0108 datasheet.

 

Refer the datasheet of TXS010X for more detail about the pull and pull down onfiguration for TXS010X series.