I personally really like Nuclear Power's tester, purely because I like seeing people turn green, red, and blue. If it's possible to expand that to apply to other maps then I love this.
In terms of actually gameplay though, I have mixed feelings. I think traitor testers make the game stale, but they can be interesting with proper counterplay. Wink mentioned a lot of interesting variations on testers, and I like those a lot. Outside of that though, basic testers that only offer the traitors some jihad opportunities are very boring to me. Innos grouping up is good for jihads, but makes actual gunfights a lot more difficult for the traitors. The innos also only need to group up for a short while, after which they can spread out and watch the tester from afar.
With all that said, I think this change could have the opposite effect. If I can test alone or with one other person and the entire server will know I'm proven, then nobody needs to group up at the tester. I'm neutral, maybe leaning negative on this change. I'd be very curious to see how it changes the gameplay, and solely for that reason I think it could be an interesting mixup sometime. However, I don't enjoy the gameplay of testers generally and I'm not too keen on the idea of buffing them.