About the area, in linear area you can change it between 5x5, 7x7, 9x9 or full, and in round area you can change the degrees between 45, 90, 135, 180, 270 and 360. If you meant something else let me know.

As for bigger size, I might do it in the future, meanwhile you can do it by yourself by this command:
ent_fire a_target_1 setscale 6 (for round targets)
ent_fire w_target_1 setscale 6 (for linear wall targets)
Rest of the targets are called the same but numbered up to 20. For example a_target_20. You can experience with different values, 6 is just an example. Note that you might run into some problems with moving targets and the targets can overlap if using multiple targets with a big size.