I was hoping this was a typo and it was stp+5...
Unfortunately, if the effect is useful only for WS, then that augment is trash, not because the effect would not be of use, but because the sacrifice of what you would be giving up to WS in legs that have pretty much no good WS stats (at best, 2 STR + conserve TP + 7 Attack or Acc? Pass).
This is now a thread about how much more awesome waltz cost- is than conserve tp.
Waltz Cost- and Waltz Delay- are both fantastic. For /DNC as well.