In all seriousness I have seen seats unbolted and moved several times. Usually not a hard thing to do, just a couple of holes drilled. However, the mirror argument is a good one. I don't know how those adjust to the mirror situation. Many drivers have the mirrors poorly adjusted anyway.
If you are sitting in the seat and can cope with the mirrors now, moving the seat forward should just give you the support you need. Hope it works, any company should make the accommodation for you.
I have just the opposite problem; some trucks are just to short for me. Freightliner Columbia is one that drives me nuts.
I used to work for a school district that had some short drivers. We used hose clamps,aluminum blocks and some no skid tape to make pedal blocks for them.