Here, we can create strategies to help each other succeed in the battle frontiers for both Emerald and Platinum versions of pokemon. I need help in the Battle Factory of Platinum. Can somebody suggest a good team for me to have in Open Level Singles? Thanks.

Battle Castle Strategy: Although leveling your opponents pokémon up 5 levels costs 1 CP each, you can get from 40-50 CP per win depending on your losses. I suggest you use fast pokemon with high Sp.Attack or Attack at the front of your party to keep your pokémon healthy. Use this strategy for maybe the first three seven-match streaks so you can have plenty CP to use.

i got the gold badges or whatever they are in every place except the battle tower and my team is lucario with extreme speed and whatever other moves, as my fast pokemon, garchomp as my attack/speed pokemon, and torterra as my defense pokemon. hope that helped.

Double battle strategie-

Metagross + ditto
Regigiggas + smeargle

metagross trained for attack, and some defences, ditto trained for speed and health, reggigigas trained for speed and attack, smeargle speed and hp

Metagross knows explosion, and protect
Ditto holds quick powder
Smeargle knows transform, protect, worry seed(or that one move that swaps abilities), and dark void, holds a focus sash.
Regigigas made to sweep, with life orb

It goes like this, metagross protects/attacks ghost types, ditto transforms.
Metagross either explodes or protects, ditto does the same
Smeargle comes out, protects while the metagross/ditto explodes
Reggigas comes out, and begins sweeping after smeargle uses worry seed/swaps abilitys, to technician

Regigias finishes them off, with aid from smeargle.

As a Defensive pokemon, I think you may need something better than a Torterra. Plus, it and Garchomp both have 4x weaknesses to ice. If Lucario is gone, then you may be in trouble. In the battle tower, you should try to put pokemon on a team that can switch in on each others weaknesses. Sharing a weakness can be hazardous.

Anyway, back to Torterra. He has good defensive stats and HP, but the 4x ice weakness can really screw him over. I don't know the moveset of your torterra, but a defensive pokemon should be able to stand up against most pokemon in the tower. I usually use a Milotic with Surf, Ice Beam, Toxic, and Recover. I poison what I can, and recover off damage and launch surfs or ice beams when possible. Plus, as my lead I have a salamence, so milotic can swith into dangerous ice type moves. When Milotic has trouble with grass types, my thirs pokemon, scizor comes in. Likewise, Milotic comes in when fire moves loom.

As you can see, its important to patch up all possible weaknesses. However, anything can happen in the Battle Frontier, from hax to the oponnent having just the right pokemon. Losing is inevitable, but you should try to make a team where losing is at least prolonged