Ah yes, you still get your ASI's if you've chosen to multiclass, you don't lose them... (unless you trade for a feat, of course)
Ok, I thought so but I wanted confirmation because...
I'm not quite understanding what you're going for with #2 - You can't use your ASI to take Rogue features... you would either take the 4th level in fighter and your ASI (or feat), or take a level in Rogue 1 to be Fighter3/Rogue1.
You can't use the ASI to take class features in another class as a feat... (unless you're referencing some rule from Tasha's or other book, which I'm not using)
Yes, with #2 I am basically saying you gain a class's features in lieu of a feat (or ASI for that matter).
No, it wasn't in Tasha's...
Quick intro: Subclass as Multiclass.
Instead of gaining a subclass in your class, you gain the 1st-level features of another class (you do not gain any subclass for this second class). Whenever you would gain a new subclass feature, you gain two levels of features of your second class. You do not gain ASIs for your second class's 4th level.
Ex. A Rogue gains their subclass at 3rd level. Instead of choosing a subclass, the player selects Fighter "as their subclass" and it becomes second class. They gain a Fighting Style and Second Wind.
Later at 9th level, the Rogue gains its next subclass feature, so gains two levels of features from Fighter; in this case just Action Surge (for Fighter 2, but Fighter 3 is the subclass of Fighter, which the Rogue doesn't gain as it is a second class).
At 13th Rogue, the PC gains Fighter 4 and 5 features. Fighter 4 is the ASI, which is NOT gained as a second class, but Fighter 5 is Extra Attack, which would be gained.
Finally, at 17th Rogue the PC gains Fighter 6 and Fighter 7. Fighter 6 ASI is gained as it is a bonus to Fighters, but Fighter 7 is a subclass level for Fighter so nothing is gained.
In the end, you would have Rogue (Fighter) 17, gaining a Fighting Style, Second Wind, Action Surge, Extra Attack, and a feat as your "subclass" features.
Now, this has worked well when we've done it but can be quite powerful at higher levels.
Back to #2:
What I was thinking was similar in that instead of your feats at 4th, 8th, 12th, 16th, and 19th levels you gained the features for a second class at levels 1, 2, 3, 4, and 5 respectively.
Using the Rogue-Fighter concept, this would be a bit different as you would gain subclasses and ASI/feats still:
Rogue 4 would gain a Fighting Style and Second Wind instead of the ASI.
Rogue 8 would gain Action Surge instead of the ASI.
Rogue 12 would gain subclass features for a chosen Fighter subclass instead of the ASI.
Rogue 16 would gain an ASI (from Fighter 4). This
could be used for a feat, but ONLY this one.
Rogue 19 would gain Extra Attack instead of the ASI.
The bonus Rogue ASI at level 10 would be an ASI, but could not be used as a feat (or maybe yes???).
So, obviously NOT what you are doing, but that was one way I could see it working...
Thanks for your information!