fs^u-, pasú-

The *peku- "cattle, wealth" root survives in Sanskrit as <pas´ú->,
but in Avestan only in compounds in the zero grade form <fs^u->,
where /p/ > /f/ before /s/. This is regular, I believe. Now, the
question is this: if *peku- had survived in Avestan (presumably as
*pasú-), and assuming that it had kept the various Ablaut grades
alive in its paradigm, including zero grade (eg. in the genitive),
would it then have had been inflected **pasú, **fs^u-, etc? making it
look almost suppletive?

Torsten