I understand the reasons why they feel the need to mix things up a bit. To try and keep things feeling fresh. But to be honest, if your priority is to save money because the BBC can't give you as much as they used to, then the last thing you should be doing is green-lighting new Cyberman costumes or new TARDIS sets. It's an incompetent management of resources that could be better used elsewhere, IMO.
The TARDIS set had to be rebuilt anyway, so why not do a new design? And the Cybus Industries Cybermen look are the longest running for the Cybermen period. In classic Who they had a new look nearly every story. There's nothing wrong with a new look seven years after the previous one was introduced.
Besides, Moffat already failed in two previous attempts to redesign the Cybermen. There was no money to do it in The Pandorica Opens and only enough money to remove the Cybus logo in A Good Man Goes to War.