I'm sorry for the tone of this answer: I tried to think of a way to say this clearly but politely and I failed, so I'm just going to come out and say it.

The chances seem good that Thomas was brought in as a fixer. The "different styles" you describe aren't of equal value: nonreflective, isolated, non interacting coders write bad applications, plain and simple. What you describe as your team's "style" is really just a set of very bad habits. Everything Thomas is doing will specifically improve matters.

So my recommendation to you is not to try to figure out how to minimize his impact. If you want to keep your job, get on board with Thomas' ideas and champion them, or you'll be the first to go.

The chances seem good that Thomas was brought in as a fixer. The "different styles" you describe aren't of equal value: nonreflective, isolated, non interacting coders write bad applications, plain and simple. What you describe as your team's "style" is really just a set of very bad habits. Everything Thomas is doing will specifically improve matters.

So my recommendation to you is not to try to figure out how to minimize his impact. If you want to keep your job, get on board with Thomas' ideas and champion them, or you'll be the first to go.