A straight weapon-to-weapon swap will probably be approved by the GM, although you're not going to get any more than STR+4+3 without access to Fu powers.
The weapon categories are very,very broad. In general, you're not going to get any specific advantages from having facnier weapons, although Iron and Silk does contain some intersting rules for particular weapons.
Remember that having something more obviously a weapon might make it more difficult to carry it about in polite society.
Hand weapons in Feng Shui are very generalized, and I'd recommend keeping them that way. All hand weapons should fall somewhere between STR+1 and STR+4. Long and pointy should be in the neighborhood of STR+3, whereas long, pointy and heavy should be +4. Anything beyond that, like hitting people with a disgruntled telephone pole or a motorcycle with napalm pinstripes, should be handled as a stunt rather than a straight-up melee weapon.
If you want to do more damage with a melee weapon, then there are a couple ways to do this in Feng Shui without resorting to digging into an Arms & Equipment Guide until you find something on a table of weapons with a "better" crit range or whatnot. First, you can make it a signature weapon for +3 damage. After that, pick up some Fu schticks to up the damage, such as Path of the Leaping Storm for long-pointy things or Path of the Sharpened Scales for more general damage boosts.
If that's not enough, then you can bump up damage by increasing your primary/secondary attributes. +1 Strength obviously gives you +1 damage, but +1 Agility to raise your Martial Arts AV +1 would also do the same thing (since +1 Outcome = +1 damage) and make it easier to hit things.
Finally, the best way by far to do more damage is to come up with really cool stunts that surprises and impresses the GM. Instead of just saying "I attack him", if you say something like, "I slice his beltbuckle off so his pants fall down, which causes him to trip and fall face-first into the nuclear-powered pizza oven", and the GM gives you a +2 or +3 on your roll for being creative, that's a bonus to hit and damage.
If duct-taping a pair of arcano-kopesh blades with vibrating monomolecular-diamond edges onto the end of your signature garden rake allows you to make more creative and entertaining stunts, then that's probably a good thing. But if you're just doing it do get an extra +1 on damage whenever you say "I attack", then don't be surprised if the GM says no or gives you penalties instead. The spirit of the game is to hit people with furniture in ways they've never been hit with furniture before, so try to keep it fresh and inventive.
I just want to chime in that using stunts to be more effective is better for you in the long run than adding spikey bits to your weapon. In your particular case, a straight-up staff is probably much better for stunt utility than a staff with spikey bits on the ends. You can use the former to pole vault, for example; not so much with the latter. You're more likely to be able to keep your staff in security environments ("You wouldn't separate an old man from his walking stick..."). You can use a staff for non-lethal as well as lethal attacks. And so forth.