The question of whether to change the transposition cannot be answered without considering the question of how such a change might be accomplished. I see three ways of doing that.
1) Revise the transmission to connect the bells to the keyboard in concert pitch. This would require changing a few keys at the bottom end of both the manual and pedal, so that instead of G,A... you would have, F#,G#... Also add one small bell at the top to connect to the treble C key. On the positive side, you have a miniscule cost for one small bell, but all the rest stay in place. On the negative side, you lose the bass G, while the bass F# and G# are musically useless, and the cost of reworking the transmission would be significant.
2) Replace the entire instrument with one that is a semitone lighter. On the positive side, you would have the same keyboard range as at present, and might gain an improved bell layout and mechanism. On the negative side, it would be hideously expensive, probably requiring complete replacement of the frame and transmission as well as the bells.
3) Replace the F# and G# basses with a G bass, add a C treble, and revise the transmission to connect the bells to the keyboard in concert pitch. This alternative would be intermediate in cost between options 1 and 2. On the positive side, it retains the present keyboard unchanged, and should require minimal modification of the frame. (However, I have no idea of the practicality of getting those basses out, since I haven't seen how the frame fits into the very unusual tower.) On the negative side - well, there is that cost.
There's also the question of the temperament of the present tuning, i.e., is it well suited to changing the transposition by a semitone? If it is truly "well tempered," then it would be OK.
As far as impact on the listeners goes, I think there would be very little. You might try an experiment with a piece of music that requires the bass G but can also be played in a key that is a whole tone higher. Play the deeper version near the beginning of a concert and the lighter version near the end, without telling them what the difference is. then ask which version they like better, and why.
I have no recommendation. But costing out the alternatives would help you to decide whether it's worth the effort.
Carl Scott Zimmerman
Saint Louis, Missouri, USA - home of at least 36 bell foundries or bell sellers, 1821-1961.