As pipewelder said the base metals overlap for performance qualification. For welder qualification you can have the welders do their qualification tests on P1 material and that also qualifies them for P8 (304) insofar as base metals are concerned. If the filler metal is P1 through P11, X34, and something else (I'm doing this without the benefit of Section IX at hand) then they are good with using any filler metal in that range. If you are considering using the "standard" 309L filler (P8) for these joints, then welders could be qualified on P1 to P1 using, for example, ER70S-X wire.

As for the WPS's required, you will need to do a CS to SS procedure. The rule is, for assigned materials, that welding a CS to SS coupon allows either base metal to itself and the combination qualified using the qualified filler. So, since my guess is you don't want to use SS filler across the board, you will need to develop two PQR's at a minimum. One for each filler metal used. One for P1 to P1 using ER70S-X filler, and one for CS to SS using your selected filler (assuming it has a P number assigned the info on welder qual above is valid). You would then want to make two WPS's, one for each PQR. In the case of SS to SS you can write a WPS using the CS to SS PQR if you use the same filler.

Depending on diameter/thickness ranges/use you might find it profitable to use SWPS as listed in the AWS Pub catalog. Most of what you are asking about has a SWPS that is National Board accepted, which would make it acceptable under Section VIII, but I'm not clear that they would be acceptable under the 31.X group of piping codes. If you can use them, they are quite a bit cheaper than rolling your own. The price is probably less than what you can get the SS base materials for.