I'm doing some thought experiments towards a computer game that simulates space combat, and I want my engagements to be interesting to players but still be relatively hard-science. Yes, I know this is a challenge.

So, the aim is to make as few modifications to the laws of physics as possible to allow:

1. Easy travel between "interesting" locations
2. Travel in a timely manner
3. Combat makes sense in visual range or near-visual range

In order to achieve this, my solution is a jump drive. This allows spacecraft to instantaneously warp to various locations, and it can be used to avoid the whole "lasers at light-seconds range" issue and bring the spacecraft to a railgun/short-range-laser/missile sort of range. 

What issues are there with a jump drive that "just" moves matter from one point in space to another?