they won't do it because it's not something BMW condones. they won't warranty I'm willing to bet. and if something goes wrong, they don't want to be responsible.
if you don't care about potential consequences, try to talk to one of the techs and tell him you'll slide him a few hung under the table. sometimes techs will do work like that after hours. But I'm sure it's going to cost you....if they'll do it.
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