I am not sure which model your talking about, your link just puts me on GW home page, but I reckon you must be talking about the mordheim stagecoach, I have 2 and no they are not conducive to modification, a 50$ a pop they make a better stagecoach than anything else. For the same amount of money you could get a lion chariot, death cart and several other pieces a kit bash a really neat war altar and have lots of interesting and neat bits left over. I hope this opinion helps, whatever you decide be sure to post pictures of work in progress (wip).
Good luck steveb