Is there anything blackjack dealers could do to increase the odds in their favour?
It’s not clear whether you are asking whether there are ways for dealers to cheat the customers, or whether there are ways to offer a game that plays like blackjack but has different odds because of a different card distribution. A lot of the simplified card-counting strategies do have to do with counting cards by categories, and betting heavily only when the categories that favor the player are in higher proportion. Increasing the proportion of the other cards would reduce the favorable ones. Low cards favor the dealer; high cards and aces favor the player. See my source for a simplified counting strategy based on three categories of cards: 2-6, 7-9, and 10-A. A dealer at a reputable casino won’t fiddle with the deck to increase odds in the house’s favor. Dealers are expected to conduct the game in the prescribed manner, and the house keeps an eye on the results largely to interrupt and bar card counters. A crooked dealer might conceivably do so to increase odds in the player’s favor,