if you make the gantry like my gantry/ look at my signature, second build/ it will work perfectly at 3m span.
BUT:
-you will need 3m straight edge, not 2m. So instead of 250euros you are looking at 500-600euros. And nope, you can not build a machine like that without straight edge that spans on top of the longer rails/ Y and A/
-it will weight 250kg. Thatch not a problem but you will need servo motors which are expensive even second hand
Basically you want to build a machine like that so you have smaller machine that could do bigger jobs. Thats the reason for that setup.
I dont understand why is the problem? You only have to load it from side, so just make that side rails lower than the working bed. Thats all.