The only problem I see with that idea, is if it follows the pattern where you use an "even" amount of materia grades across all melds, then it'll wind up being more Grade IVs overall, simply less Grade IVs per type. Also as I recall reading before, Det, if used as the 2nd secondary attribute will only go as high as 22 if you take the first secondary to 44 for a total of 66 since Det will always have a lower cap regardless. However what I'm not too sure on is what the max Det would be if its used as a 2nd or 3rd secondary attribute of 3 (or more) vs only the 2nd out of 2. 33 + 23 +19 does add up to 75, but the real question will be, how high can you take Det if there's going to be more than 2 secondary attributes? That said, using 2 secondary attributes looks at 16 Grade Is, 16 Grade IIs, and 17 Grade IIIs and 17 Grade IVs if they use close to an even amount of Materia Grades per tier.

If that's too confusing, for 1st secondary, in this case being Crit of 44, 11 Grade Is before next Grade is required, then its 11 IIs, then 11 IIIs then 11 IVs. Then for Determination as the 2nd secondary of 22, you can't divide it by 4 evenly as a whole number, so it'd wind up being 5 Is, 5 IIs, 6 IIIs and 6 IVs for a total of 16, 16, 17 and 17. However, using a 33, 23 and 19 secondaries like Skill/Spell Speed, Crit, Acc and Parry, it'll wind up being 8, 8, 8, 9 for the 33, then 5, 6, 6, 6 for the 23 and 4, 5, 5, 5 for the 19. Bringing it to a total of 17 Is, 19 IIs, 19 IIIs and 20 IVs. Granted this is just a random thought I had by using what I've read in this entire thread from the first page, so it may or may not actually be true.

But I believe using Determination on your relic will wind up needing less IVs (by like 1 or 2) overall vs going with Skill/Spell Speed, Crit, Acc and/or Parry simply due to them being able to cap higher than Determination. But since I'm not going to be working all that hard at doing the Novus quest, I'm not about to math it all out right away and see what'll be the best idea just yet, also I don't have all the information I'd need just yet to make that choice either.