I think it has to depend on context: which suits has been bid and is the player in turn limited or not?
Since a GF has been established we at least don't need a three-level preference as NF. In one of the books about the Swedish standard system they list the following sequence: 1H-1S; 3D. Opener has shown a strong hand with at least 5-4 (but in some version of the system it require 5-5). Now responder have the following options:
3H = Not forcing.
3S = GF, 6+S.
3NT = To play.
4C = Slam invite with heart support (the 1H opening could have been a four card suit).
4D = Slam invite.
4H = To play.
4S = To play.
Anyway, back to the real question
If you want general guidelines I think that maybe we need to consider how many suits that have been bid: one, two, three, or four.
One suit:
Here I guess the bidding has gone 1X-1NT; Gazzilli-Positive; 3X (or similar GF auction). Opener has shown a one-suited strong hand and responder is limited. Responder's options:
Skipped suit = Stopper showing or value showing with slam interest (like HHx).
3NT = Suggestion to play.
Raise of minor = Slam invite.
4C when opener's suit is a major = Slam invite with major support.
Raise to 4M = To play.
Other = Natural, own long suit.
Two suits:
Either both players has shown one suit each (in which case opener has probably bid Gazzilli and then shown a one-suiter), or responder has bid 1NT and opener has shown a big two-suiter.
Here your scheme could make sense nullve. Though I think that you probably want two ways to raise a suit: slam invite and "weak"?
In the case of opener having a two-suiter one option could be that a preference to the first suit is slam invitational in the SECOND suit, but that's a convention begging to be forgotten. Probably makes more sense as unsure of strain (NT or not).
Examples:
1S-1NT; 3H (GF)--
3S = Slam invite in hearts.
3NT = To play.
4m = Natural long suit.
4M = To play.
1H-1NT; 3D (GF)--
3H = Slam invite in diamonds.
3S = Skipped suit. Show stopper, but no club stopper.
3NT = To play.
4C = Own suit.
4D = Maybe some kind of specific slam invite.
4H = To play.
4S = Splinter, diamonds support.
1S-1NT; 3C (GF)--
3D = Natural.
3H = Natural.
3S = Slam invitational in clubs.
3NT = To play.
4C = Special slam invite.
4DH = Splinter, clubs support.
These assume that responder would have supported 1M instead of bidding 1NT. It is harder if the auction has started something like 2C-2D; 2H-2S; 3D (strong 2C followed by waiting and Kokish and now opener have Hearts + Diamonds and responder hasn't shown anything).
In the case of opener having shown a one-suiter I think that a rebid from responder should be natural. A raise of opener's minor is a slam-invite and new suits natural. In the case of 1H-1S; 3H (GF) then I guess 3S should be natural, 4C slam-invite and 4D natural (no way to show clubs).
Three suits:
Now opener has shown a two-suiter and responder suit of his own. Most play that responder hasn't denied support of opener's first suit. Luckily its pretty easy since opener's second suit will be a minor and responder's suit will be higher than opener's suits.
Preference = Real support. Now 3NT is non-serious.
Rebid = Natural.
3NT = To play.
Minor raise = Support, at least mild slam invite.
Fourth suit = Stopper asking if at three-level. Otherwise I'm not sure, perhaps some kind of general strength slam try?
Four suits:
This isn't very common, but could happen in an auction where fourth suit forcing is raised (if that's natural in your system):
1D-1S;
2C-2H;
3H--
These are murky waters indeed, since in many systems fourth suit forcing is the only way to go if we have a slam invite. Here your scheme could make a lot of sense nullve, since every suit is a possibility.