[i](There are no stupid questions - it's just that those are the easiest to answer.
This, however, does not fall under that loose umbrella - if it did, we wouldn't be on page 2. )[/i]
If you're going to go w/ WW, there is no need for any increase in magnitude:
o Step 1) The maga invents a Ritual spell (in this case, a CrCo healing Ritual).
o Step 2) The maga has the Ritual spell Watching Ward at sufficient level to cover #1, above.
o Step 3) The maga casts both, spending the vis for both - done.
The result is the first spell (the CrCo Ritual) , with a trigger of her choosing - possibly "drinking the potion", altho' something even simpler could work, such as "breaking the seal on the potion bottle", or similar w/ any object. No need to mandate "consumption" as the trigger - at this point it could even be "the target's body receiving a Light wound or greater" - a perfectly valid trigger, afaics. The trigger could be simply to say the magic phrase "OMFG Heal My Ass!" - the spell does not have to be located in anything physical, it has been arcanely attached to the "target", the grog/companion/whoever, the eventual recipient of the Healing.
So I don't see any need for additional mag's for "delay" or complexity - the double-Ritual requisite will cost enough vis that it will be used rarely (depending on how much vis you give away*). This could work fine for any spell (= or < the Lvl of the WW) - Ritual spells are just more expensive re vis.
Worst Case Scenario?... I'd be breaking my own rule! It is (apparently, as it currently is interpreted) within the Rules As Written, so there's little to do against it, but... I'd say that the Worst Case would be to grant the ability for a non-mage to cast a spell on themselves when they need it. They could NOT "target" or "aim" that spell - remember, we are assuming the "target" of the Watching Ward spell is the grog/companion, so Range:Self. But Leap of Homecoming, or Cloak of the Phoenix, or something similar where the "target" is ground zero. The worst case, then, would be something in the direction of a huge area-effect CrIg spell with the "target" being somehow immune (a Rego requisite, or just a hole in the area effect while all around them suck it up).
But that can be done with the current RAW, so you're losing nothing by allowing this.
- Regarding the whole "game balance" thing...
Think about what is fun for your Players, and what is fun for you. Both have to be maintained to achieve a successful and long-lasting Saga. You don't want to shut down "creativity", but you (probably?) don't want to allow "creativity" to be an excuse to rewrite the rules, either. As written, this "potion" (or whatever form it takes - doesn't need anything physical, it's just a spell attached to a target) will take maybe 10 vis, 5 for the CrCo and 5 for the ReVi - that's pretty damn expensive as it stands, doubly so for what the Characters get in return! You can change that "expense" by giving away vis hand over fist - or, you can make it completely unattractive by giving away almost none.
These are the "game balance" decisions that you, as SG, have to make, and have to try to foresee for the longer story. Don't go overboard all at once, but err on the side of generosity. "A little extra" will rarely break the game, but "never nearly enough" might easily wear on the Players. As an experiment, you can give away "a lot" and watch and see where the Characters go with it - it never has to happen again if it's starting toward imbalance. Meanwhile, your Players will have had their "intermittent positive reward" and be happier with the game - and you can repeat rarely, as the need occurs, and have a better response than if vis fell from the sky down like rain.