i would think that you 1) need to show good specs... check out
www.armytechnology.com for that
2) you need to get good pictures = getting permission.
3) try to use good stories, and interesting facts, like how the weapons were used, or misused, the pros and cons of every vehicle, a short history...
and 4), what i notice no book publishers do, is try to talk about each vehicles different mods, as many as you can...
e.g. i like reading about IDF, all i see at most is merkava 2, 3 and sabra... they hardly talk about it to the degree of
www.israeli-weapons.com, and when they have american M113 and M60's they never show newest mods...
my newest book however has helped, it has some good info on Sho't tank as well as centurion.