But you wouldn't lose your high gear if you put an 11/34 on in back. 50/11 isn't very different from 52/12. What you lose are the tight increments between gears, or in other words the gaps between gears would be larger. But the advantage is you cover a wider range of gears in a single ring, avoiding front shifts on changing terrain.

But it sounds like you love your triple, so probably this isn't the bike for you unless the shop would be willing to swap out the components for what you want.