Using an exfoliate is a wonderful idea, though I've only ever used them in soaps I've made. Using them in a moisturizing bar is a great idea though you'd have to wipe them off afterward!
And lavender essential oil is a great one to use. you might think about combining it with Tea Tree Oil, too. TTO has antibacterial qualities and helps to relax sore and aching muscles. It's a wonderful additive to bars, creams and lotions. It has a rather strong smell, which might overpower the smell of your lavender, but it's healing qualities are second to none. I keep a bottle of straight fractionated coconut oil infused with drops of peppermint and tea trea oil by the bedside for my back and my wife-bot's arthritic hands. She often wakes in the morning and cannot even move them. Then I have to run in the FCO with the TTO and the PO just to get her hands to work. And it works! Such a simple remedy!
As for the beeswax, I would stick with between 5% - 8% of your total concoction. Above that and it can get waxy and can act as a barrier for your carrier oil and its precious canna cargo from entering the skin. The more beeswax you use, the less effective your pain relief will be.
Try considering using some thicker, solid oils into your product. Maybe Shea Butter. It is one of the best skin loving oils around. Helps t heal cuts and abrasions (I have personal proof of this) and helps to support your carrier oil in delivering its precious cargo to the muscles. The problem wth SB is that it can be a bit greasy if you use too much. I'd stick with between 2% - 5% MAX for SB.
After SB, if your concoction is too soft, still, try using LARD!
WHAT??!!? LARD? ARE YOU MAD? SICK? TWISTED?
Consider this: When settlers were learning how to farm this great land (yes I know I'm Canadian, but we had settlers too), they had no access to coconut oil, shea butter, grape seed oil, pumpkin seed oil, etc etc. Now did they? What DID they have access to? Lard. Easily produced on the farm and sold into the cities, it was used to concoct night creams with the addition of beeswax and borax to emulsify it into a smooth, creamy concoction that moisturized their dry skin (from farming the great western lands where it is very dry environment), cooled their faces, soothed their raw skin and generally was a wonderful all around moisturizer. They didn't use fractionated coconut oil, they didn't use regular coconut oil, they didn't use grape seed oil, they certainly didn't use precious olive oil. No. They used lard. An oil that was easily produced on the farm and was kept in the larder, which they had access to.
Test this out: Stick the pad of your finger onto a bar of lard and pull away the tiniest bit of it. Smooth and rub this lard into the back of your other hand and rub it there. Let it sit. After about 5 - 8 minutes, test the feel of your skin. It will be silky smooth, glass-like almost, and wonderfully moisturized. I asssure you, you will be shocked.
We cringe from using animal fats because we've become so accustomed to using only vegetable oils for our concoctions. But if you want to produce a cream or body butter that remains relatively solid at room temperatures, then lard might be your answer.
And if you STILL don't trust me on this issue, then produce a small batch of concoction using about 20% - 30% lard as one of your carrier oils. Work with it. See how it works. Feel it. Test it. Try it. You might be pleasantly surprised.
WARNING: Do not even TRY suggesting this to a vegan client!
They won't be happy about it.
It always troubles me how the healing knowledge of ages past gets lost through misinformation, prejudice and cover ups...
Yes, the oil already extracted from the seeds. I looked into extracting that oil myself....ah ....no. I'll just buy the oil. 
