I like it, but the pylons might be way vulnerable for a tactical shuttle. I'd fill up the space between the hull and the pylons, it'd make the shuttle more sturdy and less likely to lose a nacelle when it crash-lands or slams into something. Maybe merge the nacelle into that area between the pylon and hull, just like how the defiant has them integrated also. When I hear tactical, I think sturdy. Something like:
I like it! I've always thought that Starfleet ships, especially shuttlecraft, should have a bit more variation in their liveries.
I think you need to determine what its purpose is first. What is it meant to do, to fight, to support, in what situations, and environments, for how long?
Tactical Shuttle says it all.. It's able to fight and deploy small elite tactical teams anywhere necessary.