Posting to say I think Swords Dance and Dragon Dance are both very viable options that should be considered, Dragon Dance especially. On the physical offensive side, this thing really has pretty terrible stats, and while this is compensated very well by his extreme bulk, I really doubt he will be too much to handle especially considering his Stealth Rock weakness and susceptibility to Sandstorm. Also, a Dragon Dance set will pretty much pretty much ALWAYS be walled by Heatran. I don't think Rock Slide would really be all that much of a stretch, because come on guys, it's 75 BP on a Pokemon with base 70 Attack. So what if it hit counters super effective, it's still probably doing next to nothing unless on a designated physical attacking set.
So yeah, the reason I like the idea of Dragon Dance and Swords Dance is that while they are certainly not overpowering (well, I would say Dragon Dance at least), they atleast provide this pokemon to have atleast a little bit of unpredictability about him. Basically, I think most everybody would agree that there are MUCH better Dragon Dancers, so that really isn't an issue, more so that it "counters" his supposed counters, but this is similar to many other pokemon. They can counter their counters, but in doing so they use a less useful set and are of less overall benefit to the team.
Swords Dance I concede may be a bit much simply because of the high base power and reliability of his physical STABs, but like I mentioned earlier, his lack of physical coverage could make it a possibility. I like Fishin's idea of possibly making Flare Blitz + Dragon Dance + Wood Hammer illegal through Charizard or something, and I think that's something to consider.
Basically, like a few people have said, I think it is much easier to add a move now that could possibly be removed later than doing the opposite later. In the end I think his physical options will have little consequence considering how much better he is at being a defensive pokemon, but it just seems like now we should be giving him anything that doesn't seem completely ridiculous, with the knowledge that anything that is really a problem can be dealed with later. Obviously we want to put a good deal of thought into his movepool, but really I think testing is the only way we can see if something like Dragon Dance or Swords Dance is really broken.
Also, to people freaking out about giving him these low bp Special attacks which hit his counters super effectively (I'm looking at Charge Beam mostly), remember that this will almost definitely be recieving Fire Blast, which will most likely be doing ALOT more in neutral hits than something like Charge Beam will be doing with Super Effective hits.
Edit: and @Karrot above me: The problem with that is that his attacks aren't that hard to resist because of his lack of attacking options. Fire / Grass is good coverage, but not great. He will never beat Heatran without HP Ground, and with HP Ground he won't likely ever beat Salamence, and will have major trouble against Gyarados and Garchomp, especially since he will most likely have taken 25% damage coming in, making him easier to kill. I admit that he would be pretty good, especially since most Phazers are not able to switch in, but I think he is kept in balance by his bad type coverage, and if even then it is too much, it is very easy to make Wood Hammer + Dragon Dance illegal, opening the door to many, many more counters, if he was limited to the weaker Seed Bomb. In the end I think it just creates one more viable option for him to mess around, which as far as I see it is a good thing.