The only problem about more enemy moves is that the battle is harder, or it's harder to avoid damage. But you'll have to risk it. If you choose fast characters like Trishtan an Kika, all leveled, making Rene the slowest character, you'll have virtually no chance of getting the 2 dig items within 100 turns. I mentioned Eugene and Dario (or Sigurd), but Nalleo and Dario is fine, even better when underleveled, very good idea. If you wanna get both dig items, I think you'll not save time by going for the western one first.
I'd say ignore the gale rune dig, just make a note in the video like "You can find a gale rune with Rene in the western corner, but it's not too important". Then, for example in Terana Plains, you could write "We'll go for the dig item near the merchant; it's a wizard orb, a rune that will be very helpful when going for S-ranks". After all, it's about S ranks, not any useless dig item. Maybe I'm wrong, but I believe most players only care for S-rank items and rare/powerful stuff. Moreover it's impossible to get ALL battle items anyway, because bonus reward items and S ranks are often times virtually mutually exclusive.
"Within the four seas, all men are brothers" Shuihu Zhuan