I didn't know the team order can be changed during the team preview.
You can. On Wifi, you can select the pokemon you want to use, in the order you want. Sadly, this often leads to noobs using only 1 or 3 pokemon instead of 6, even tough there is a clear indicator at the bottom of the screen saying how many pokemon you can select...
In fact, on the old BW Zoroark analysis there was a note detailing how to mount the team on Teambuilder and how to shuffle it around before battle. This is never seen now as Zoroark is easy to spot anyway thanks to the minifigures that track the HP and status of the pokemons, but that's besides the point.
By the way, it would be cool to enable an option to use less than 6 pokemon (which you can also do when selecting either of the stantard 6 vs 6 rules on Wi-Fi), and get bonus points for winning with incomplete teams; but that's another question entirely.
Plus, even tough it may sound incredible, there might be times you prefer to not have certain pokemon, normally on teams that only can prevent your main wincon, let's say Volcarona, from sweeping by setting up Stealth Rock and phazing it out until it is too weakened to sweep. In this case, you go solo with Volca and win.
Similarly, let's say you face a full stall team. You have a fragile scarfer like a physical Greninja Protean that won't be able to do anything there, and if it comes out on a phazer like Skarmory, the stall team gets a free turn that can cost you a lot of time, thus you better bench him.
A good option to enable Team Shuffle and <6 pokemon teams would be: have the six images of the pokemon in a row, from left to right as usual. You can drag them left or right, and by moving it over another pokemon, they switch places. Below the pokemon, there are six squares. You can tick or untick them to select the pokemon you want to use. To prevent the Wi-Fi problems, the squares are ticked by default, and to be able to use them, you must enable it in "options".
Another option that should be enabled, is to be able to have less than maximum PP on moves. It might sound absurd, but there ARE some situational moments where this might have some use, ranging from gimmicky (Trump Card on low ladder troll teams) to legitimate (being able to use Struggle earlier to get a last second kill on a pokemon carrying a way to recover HP passively and high attack like Poison Heal Swords Dance Gliscor, luring a Dugtrio with choiced Thunder)
