Can command blocks teleport the a person closest to a set of coords instead of the command block itself?
Solution 1:
Yes, you can. It's pretty simple, use the following code:
/tp @p[x=0,y=0,z=0,r=0] *tp coordinates*
Where the values x, y, z define the center of the search (the player nearest to these coordinates would get teleported) and r defines the radius of the search. If you don't want to limit the radius omit r.
Do not use decimal values for the search center, this will not work.
See here for more info.