I do RV detailing here in Florida. I do not (nor would I even attempt it) remove 3M or Diamond Shield film. However, I know of a company that does this sort of thing and they use steam... it takes them 1 to two days. They do not guarantee for any clear coat of paint damage. They charge around $1,200 to do this.
Once it is off, most likely you'll have to have it inspected for either a paint touch-up, or complete front paint job where the film had been.
Bras (in my opinion) would not even be used, and here's why. While traveling down the highway, these bras move rubbing up against the paint acting like sand blasting. Dirt and moisture collects underneath and creates a sandpaper-like abrasive. I have heard many people say that they have never had a problem with bras, but after a quick examination I point out areas that they seem not to really care about. Many owners are quite finicky about their paint and you won't find a bra on a finicky RV owner's coach.
One of the best products to use on the front of an RV is something like Liquid Glass or Rejex. Both can be purchased at most hadrware stores. One more option would be a product called Opti-Coat 2.0. This is taken off their website and is well respected throughout the detailing world.
Opti-Coat (Opti-Guard) is a hard wearing, aftermarket, ceramic clear coat for superior resistance to scratching (9H) and chemical etching from environmental impacts. It provides permanent protection for all factory paints, and can also be applied to exterior glass, metal and hard plastic surfaces.
Opti-Coat is not a wax or sealant like other products on the market. It is a ceramic clear coating very similar to factory type clear coats. A layer of Opti-Coat measures approx. 2 microns in thickness, or about 100 times thicker than your typical wax or sealant. Unlike paint protection sealants such as PTFE, Nano Sealants, GlassPlexin that degrade over time and are easily removed through washing with water or chemicals, Opti-Coat does not degrade and cannot be removed by chemicals such as heavy duty truck wash or even caustic degreasers. It is totally resistant to these chemicals and produces a permanent film that is chemically bonded with the factory paint layers. Opti-Coat is effectively the vehicles new outer clear coat. It is far more resistant to chemical etching than factory clear coats and far more resistant than competing paint protection sealants. The 2 micron layer also provides a thick buffer between any damage and the factory paintwork.
This is the same stuff that dealers use when you pay for that lifetime paint protection barrier even though we all know, nothing lasts a lifetime. This product is generally applied by experienced detailers, so you may be able to find a local detailer around your area.