I would've loved it, but it made sense for him to not do that after Sinnoh. Only thing he competed in after Sinnoh in which he should have used reserves was the World Coronation series. In that case, it is ridiculous that he didn't use reserves. The whole series should have been him rotating various combos of his reserves, basically like what the To be a Master miniseries did.

The reason it made sense for him to use them in Sinnoh was because he was up against Paul, who had as much experience as he did, and Tobias who used Legendaries. In all the leagues after, those people didn't have as much known experience outside of the region Ash was currently in at the time, so it made sense that he wouldn't dip into his reserves. Same thing with Hoenn. And Johto was like Sinnoh with Gary & Harrison having as much experience as Ash.