Probably possible, but don't suppose it happens much.
Plenty of line captains become LTC's without having been a SFI/TRI, but obviously you need the TRI to become a TRE.
Normally, like most things in RYR I guess, the normal procedure is to go from SFO with SFI, to Line Capt with TRI, LTC then TRE.
I know lots of Captains who joined RYR via direct entry, who were TRE's at their previous company who keep it valid at their own expense and don't exercise it for RYR.