Why are you hiring people that you don't trust?

If you don't trust a developer enough to give them admin access to your site, then why would you install any plugin that they built for your site?

There's also the issue of cost as well. If I'm developing a wordpress plugin for someone then I don't mind if the client restricts my access and requires me to things in an indirect way (And frankly, I'd prefer to work on a staging server: there'd be much less chance of making expensive mistakes). But it'd take the client longer, and probably increase my hours. Which is fine, as long as the client has the budget.