Plenty of trailers in your size range that will tow just fine behind a properly equipped Ecoboost. I agree with the OP's sentiments about not wanting to drive a 3/4 ton on a daily basis, especially where there is an option that will get it done and probably get better unloaded mileage.
And I guess I disagree with buying a 3/4 ton in case you end up wanting a bigger trailer. I know a lot of people who are on their first trailer many years later and never got the 'upgrade bug.' Plus, who knows what you're going to want to do in a few years. Maybe gas prices triple and you don't want to RV anymore, or you want a smaller trailer instead of a bigger one. Maybe you have health or financial issues and you can't. Maybe you find another hobby.
I know that for us, our outlook on RV'ing has changed at least 3 times over the 6 or so years we've had our TT. In some cases, spending more 'just in case' only results in spending more!