The frame part is easy, just use sliding or rocker dropouts. You could also build it with a 44mm head tube and use an Angleset headset to change the head tube angle a few degrees. In reality, it is only going to feel different for a short period of time, until you adjust to the handling difference. Anything different from your current bike is going to feel weird and wrong at first and then you will adjust to it and that will be the new normal, providing that you don't go too far outside the normal range of lengths/angles/offsets.