Combining Passives from her passive and W sounds really good, it's certainly a smart move that makes sense!
Not sure about moving the ultimate to her passive though, then it becomes a lot like Aurelion Sol's E (is it E? I can't remember which ability it is). I'd want things to change a little differently. I've tried to preserve some of her current ultimate in my suggested new one, see "casting E during the ultimate" in the descriptions below.
Valor is supposed to be a cool bird that helps her fight but his only presence in her kit now is as a single skillshot on her Q and as a glorified taxi on her ultimate. It really takes away from the tag-team with bird companion that is promised by her design and lore. I've tried to rework her in a way that gives Valor more of the spotlight, while making them both feel like more of a tag team.
If I had my way, I'd make the following changes:
Core: Make it so that Valor is always present. When no abilities are cast, he can stay by Quinn's side, flying around her or landing on her shoulder.
Passive: Give her more ways to apply the passive mark with her abilities (see kit below) and take away the randomness of her passive mark so that it can only be applied by abilities. Reason for this being that it will feel more impactful and more like a tag team if you control how the marks are applied. It would feel more skillful, Quinn wouldn't have to wait or play complicated vision games to try to control the mark, and opponents would not have to fear being 'cheesed' by the passive marking them and then getting followed up on by Quinn's undodgeable E.
Q: Make Valor dash from his current position, be it Quinn's side, or while circling an area during Quinn's W. (See below) After striking a target he returns to her side.
W: Move W passive effects fully to her actual passive. On cast, Valor flies to the target location and then begins orbiting Quinn at that distance. Marking enemies (or the first enemy - for balance's sake) he passes over periodically, and granting vision in an AoE around him. After X circles he returns to Quinn's side.
E: No change, Quinn's vault ability is the coolest thing ever and it feels really good to use. I wish I could make it available more often but that would be OP. This ability is really fun as is.
Ultimate: On cast, Valor becomes excited/enraged (gains a resource bar) and swoops across the battlefield (like a Rumble ultimate), attacking the first target struck, damaging and incapacitating them for X seconds (Something short like 1/4 or 1/2 second) while they reel from the strike. After striking the enemy Valor orbits them at a close distance, looking for his next opening to strike (strikes again after X seconds, repeating until he is "tired"). After taking too many actions, Valor uses up his energy and becomes "tired," retreating to Quinn's side.
If more counterplay is needed, it can be made so that Valor's resource bar can be reduced by enemy attacks (like ward health)
- Casting Q during the ultimate will cause Valor to swoop from his current position, but instead of reducing the target's vision, he will simply reapply the ultimate's incapacitation for the shorter duration provided in the ultimate's description above. Dashing will consume a portion of Valor's energy, making him more tired.
_Important to note, this could be used to move him from an enemy (like an Oriana Q) to attach to another enemy or to reposition him for Quinn to dash to with her improved E (see below)
- Casting W during the ultimate would cause valor to fly upward (and stop attacking his target, obviously), and orbit similarly to the original ability (Maybe it should be allowed to mark more frequently. Circling will consume valor's energy over time, eventually making Valor "tired."
- Casting E during the ultimate would work like normal unless she targets Valor, doing so will cause Valor to catch her and carry her, granting her bonus movement speed for the duration. Valor loses energy as he carries her, becoming more "tired" the farther they travel. If recast, Valor will fling/drop her, causing her to dash in their direction of movement and vault off of any enemy struck. Using the recast will consume a large portion of Valor's energy. Standing still for .5 or 1 second will cause Valor to set Quinn down, ending the effect.
IMO these changes would increase their interactions and make you really feel like a tag-team with Valor.