David Garrard frequently rushes the ball. Byron Leftwich did so with some consistency, but not as much as Garrard, and Mark Brunell certainly wasn't what I would call a rushing quarterback. I honestly don't know anything about the offensive coordinator, but their current offense seems to be based around a mobile quarterback. This isn't to say that the Jaguars are definitely going to use Tebow as another rushing threat, but the team has seemed to operate that way for the past few seasons.
If they attempt to take Tebow out of his element, as well as take the team out of its element by adjusting to a more pass-friendly offensive scheme, then they may still run the risk of injuring him due to inexperience/discomfort with the offensive scheme/whatever you want to call it. Once you've had a rushing quarterback for a few years, you get into a rhythm with that style of play. Even if we assume that Tebow won't be rushing, those 42 sacks that Garrard took still suggest to me that, regardless of the scheme, he's going to be in danger of getting nailed by experienced professional athletes.
Of course, all of this assumes that he even goes to Jacksonville and gets to start over Garrard. Given enough time to adjust to the pros as a backup can advance his career, but I honestly don't see him growing as a player at Jacksonville if they don't turn things around quickly. Art Schlicter, Gino Torretta, Andre Ware, Carson Palmer and Jason White are just a few college quarterbacks whose starting careers ended (or were delayed) due mainly to (in my opinion) playing for sub-par teams that couldn't give them the opportunity to play with and learn from quality athletes and, in many instances, couldn't protect them from quality defensive athletes.
This isn't to say that there wasn't more going on than just an inexperienced team being unable to teach and protect these new quarterbacks; there were certainly other factors. And this isn't to say that Tebow won't thrive in the NFL, or that he won't thrive with the Jaguars. It's all speculation from me at this point, but I just think that the Jags don't have the coaches or the talent for Tebow to grow as a player, and if he does by some slim chance get to start over Garrard within his first or even second year, he will likely be injured.