[Bridget]

The general idea is that you deploy the sentry. It looks like a level-3 sentry. It has the statistics of a level-1 sentry. The longer the gun stays up, the more powerful it gets, eventually becoming as powerful as a level-3. Now, I think this encourages positive feedback. If the offense flows well enough, they can lock down an Engineer with a poor sentry gun. If they slack behind, they end up letting it gain power.

There's always the problem of offensive Engineering coming from a single-level idea. I think something like this would prevent that. If you drop a sentry in front of a spawn, with people constantly coming out of it, it will hardly ever have the time available to build up power. The only problem I see from this is people getting mad their gun isn't an instant killing machine. The pickup community would especially find it frustrating.

You could keep levels with this suggestion, but I think it's redundant still. Plus, Engineers would be confused as to why their guns are magically changing form for seemingly no reason. Plus, you would need animations between level-changes for it to make any sense.

You guys could just add a bar over the SG that slowly filled to show its progress. The idea here is that it's upgrading, but can still fire and protect itself while doing so. It simply automates the hard work.