How about when you build the weapon, it stays as a floating dispenser that just heals you (not supply metal). But it has an ability for you to manually control it (But only if you're out of spawn). It can also not activate doors. When you manually control it, it changes your viewmodel to the R-CAT's. There you can see what the sentry is seeing in first person. Equipping the Wrangler will give it 1/3 of damage taken, as well as a faster firing speed. However, to balance things out, activating the sentry will leave you 100% defenseless until you return the sentry to you. It cannot return to you on its own and will shut down and stay there until it is either turned back on by you or you're killed. Being killed would automatically destroy the sentry.