I think using the tower to transport energy would cut allot from the game. I personally enjoy the amount of different moving parts you're required to create and looking at how other player's rooms function is in my eyes amazing. Everyone has creeps that mine, carry energy, upgrade, build, repair, attack, ect and adding turrets that can almost do everything except harvest it's own energy would take away allot from the game. People would just need a harvester with 5 work parts to power the tower and maybe a few others to fill the spawns / extensions. Go from this finely tuned, nice looking, complex game to the "search for the newest room with 2 energy near it's center".

P.S use links if you want "creepless" energy transport.