Trademarks don't work like that. When you have a trademark, then somebody else can't have a trademark that is confusingly similar to yours. So you can't trademark "Bomb Shell" if somebody else already has some iteration of "Bombshell".
I believe that once you file for and are allowed to use a trademark, you have to use the trademark a reasonable amount of times.
Not exactly. Hasbro only adds Autobot or Decepticon to the front of names when they want to strengthen a trademarkable name that may not be strong enough on it's own, either lack of recent usage, or (more likely) because it's a common english word. Ratchet, Jazz, Brawl, Skids are difficult for Hasbro to defend in court, so they stick the made up word like Autobot in front to make them stronger trademarks.What companies will sometimes do when this happens is to modify the name to get around it. For example, "Autobot Jazz," "Decepticon Brawl," "Autobot Ratchet," "Cybertron Perceptor," "Decepticon Frenzy" et al. Now sometimes simply adding "Autobot" or "Decepticon" to the name isn't enough - all depending on the nature of the toy and the copyright being held by the current holder.
If somebody holds a trademark, you can't simply just stick "Autobot" or "Decepticon" in front of it and call it a day. That's why there's no "Autobot Hot Rod" or even "Autobot Hot Rodimus".
From what I understand, Aaron Archer said the reason why they went with Meister was that they felt three releases in a row (Hound, Tracks, Jazz) with "Autobot" as part of the name sounded kind of lame and redundant, so Meister was used as a substitute. Also, Hasbro was still hoping they would be able to release the Porsche and use "Autobot Jazz" on that.For example in most TF lines Hasbro are able to use "Autobot Jazz" but they weren't allowed to do this with Alternators - possibly because Alternators is also seen as a model car line, not just an action figure line, and the name "Jazz" probably already belongs to any toy company producing a replica of the Honda Jazz. As a result Hasbro used Jazz's Japanese name "Meister" for the Alternator.
Lanard (makers of the GI Joe-like toys The CORPS!) held the trademark for Shockwave for a number of years, which was why Hasbro resorted to Shockblast. Hasbro was able to resecure Shockwave when Lanard abandoned their attempts to register it, and Hasbro slapped it onto the Cybertron redeco of Armada Terradive. They were actually aware of the trademark being available back in 2004, but at the time Alternators Shockblast was already well underway, so they couldn't change the name.This was probably also the case with Shockwave, unable to simply call it "Decepticon Shockwave" they called him "Shockblast" for Alternators and Energon. Hasbro also cannot use the name "Devastator" for Transformers but they can use it for Star Wars, as Lucas currently owns the name (it's the name of a Star Destroyer) - I'm guessing that could be why Energon Devastator was called "Constructicon Maximus" and movie Devastator was called "Decepticon Brawl."
So guys, don't complain when Hasbro slaps seemingly random G1 names onto toys that don't really fit. They need to do that to keep the names in usage (especially right after they are able to resecure the trademark).
The reason why Hasbro uses "[Insert word] Devastator" is because Hasbro's legal department considers Devastator to be too difficult to defend in court due to it being a common word. Movie Devastator was renamed Brawl because both Hasbro and the screenwriters wanted to save the name for a gestalt.
As far as I know, Lucasfilm does not hold the trademark to Devastator for the same reasons (too difficult to defend in court), for to my knowledge, there are no products called "Devastator" from the Star Wars merchandise lines. To hold onto a trademark, you have to use it, and Lucasfilm is unlikely to trademark Star Destroyer names given they mostly use generic naval names of common words.