That is a good idea, I like it.
Everyone would be able to build the Tier he likes and getting the style which is preferred.
Further it would lessen the cost of upgrading the same Tier, happened to me as I was Building the main Tower out of Khitan first and then had to tear it down to build it out of Aquilonian.
With your idea I would just have to re-dress the fronts which would lead to me being able to use all the same Tier troughout my base, currently I used every Tier due to the style it presents.