I am currently using my Lv74 Weavile to fight through Platinum's Battle Hall:

Weavile @ Life Orb / Physical Sweeper
Jolly / Pressure
252 Atk / 6 Def / 252 Spd
- Ice Punch
- Night Slash
- Brick Break
- Aerial Ace

I just won my first battle with Argenta and was awarded the Silver Print. I currently have 26 BP. I am still saving up for a Choice Band.

I have completed the Grass and Dragon type battles and started fighting through the other types, except for Fire. How should Weavile fight his way through Fire Pokemon if he can't land any super effective hits on them for the time being? Weavile's defences are very weak and he has been close to being KOed by an Anorith with X-Scissor in the Bug section. Fire attacks will probably hit even harder.

I also lost using Weavile, against the Fire or Fighting sections (I forget which).

I believe using a more tankish attacker may be beneficial in Battle Hall. You could also try to use Focus Sash and Night Slash to 2HKO opponents.

You can use Dig if you like. Other than that the only move Weavile learns that is SE against Fires is Surf.

I don't know the Battle Hall too well, but can't you just try another Pokemon for that? Bulky Gyarados can take care of Fires, as well as Rocks and Grounds.

I might just start over with a different Pokemon then. I really don't want to alter Weavile's TM-expensive moveset.

I do have a lot of time and I'm just aiming to save up on BP to buy useful hold items.

When ever I go to the battle hall I start againest the types i have the most disadvantage
example: kingdra
1st Dragon
2nd Flying
3rd Ground
4th Psychic
5th Water
This way as the battles go on by the end I'll only have to Face pokes i have an advantage againest.

Gyarados would then have to defeat Electrics such as Jolteon which outspeed it easily.

You can always change the moveset to accomodate different types. Kingdra is a nice example, as you could use a Dragon move for Dragon types, then switch to an Ice move for ice types, etc.