Even though the minor virtue is a decent solution we wanted to try to make a major virtue that would work in our group. This is what we came up with, if you have any thoughts on if it seems reasonable or if there are flaws we have missed, please share.
Our suggestion, with some variants is:
Major Secondary Insight
Your method of magical study is especially versatile. When you spend a season studying one of the magical Arts from a book, a teacher, or raw vis, you also gain a 1/4 of the source quality experience points (rounded up) in each of any 4 Forms, 2 Forms and 1 Technique, or 2 Techniques of your choosing, except the art studied. This xp can never raise a Form above your highest Form or a Technique above your highest Technique, and it cannot raise any art above the gain limit of the source. You may choose different Arts to receive the bonus experience points in each season, even when continuing to study the same Art from the same source. These bonus experience points are not increased by Affinities or any other factors.
In addition, when learning spells from laboratory texts, you can learn from different art combinations as if learning from a teacher, substituting your own lab totals as the teachers lab totals.
Not sure if this should be part of it too (might be to complicated):
Similarly, when doing multiple lab activities in a season you can work with different art combinations, but must reduce each lab total by the fraction of time spent on that activity.
alternatively, and less powerful:
Similarly, when doing multiple lab activities in a season you can work with different art combinations. The lowest art combination lab total is used in this case.
And finally, since both minor and major versions can coexist:
You cannot have both minor and major secondary insight.
We thought that 1/4 or possibly 1/3 might be a reasonable value here, as the character can be more focused than the previous suggestions where you have to put in your lowest art, but more flexible than elementalist, and should thus get less total xp. The thought with limiting these extra xp by source level is that a source should never give xp over its limit, even if in another art. I think this version gives more interesting decisions than putting the xp in your lowest art all the time, while still curtailing being able to put the xp in your best arts. More adapted for a generalist that uses 2-5 Techniques and maybe 4-6 Forms.
The rationale for making it easier to learn spells (and possibly imbue artifacts) with different art combinations is that a generalist will probably want to know many low-mid level spells in different arts, and the system as it is makes it very time consuming to do so.
Would love to hear your thoughts on this, and I will try to provide an example shortly to make it clear how this would work if any of the rules text as I wrote it was unclear.