OK, let's go with the basics.

First of all, though specs may appear to limit your options, that's not necessarily true. It's very possible to run derailleurs beyond the rated capacity, and many do so without ANY issues at all. But you have to know what's what.

Shift to low gear, and pull the lower chain loop froward to swing the RD cage counter clockwise as far as it will go (the lower loop will be a straight run to the bottom of the inner ring). Note the radial clearance from the upper pulley to the 25t sprocket. That's the limiting factor and you can safely use a larger sprocket figuring that each tooth will add 1/12" to the radius of the sprocket.

So if you have 3/4" to play with you can go up 9 teeth. Keep in mind that you still need some clearance, so don't go the limit. But I expect that 32t is very feasible.

Now, you have to sweat chain length and TD take up capacity. The ABSOLUTE minimum chain length is determined by looping the two largest sprockets plus 1". Odds are that once you lengthen (replace) the chain, the RD will not be able to take up all the slack using the 34t ring with the smaller rear sprockets. This isn't a crisis, and you simply won't use the crossed combinations.

The number of unusable gears depends on the extent of over capacity. If the total combination (big+big minus small+small)is 6t larger than the rated capacity, and your smallest rear is 12t, your RD will start taking up the slack on the 18t (or a bit smaller).

So, you now know the considerations, and can make an informed decision about the limits of what you can achieve.