tbh, even though i like the competitive and skill based aspects of the game, i think adding such a repeat build button would be fine.
But it needs some kind of drawback to make it inferiour to the current manual method (Maybe a short delay between each production [Maybe even scaling up with current pop or age] ).
Like how autoscouting is inferiour to normal scouting, as it doesnt prioritise scouting the enemy or key ressources.
Most players are casuals, that enjoy campaigns, scenarios or closed maps.
Making the game easier to handle and easier to have big lategame fights will have more of them play the game and maybe buy dlcs.