I've been browsing the FN Forum and it appears that another company is also making a lower for the scar 17. The guy making the new one also made an after market charging handle for the scar 17.
This guy has not released very many details about his lower, but hinted that it will take sr-25 pmags and have better ambi controls. IIRC he did mention that it would be machined from 6061. Many people on the FN forum have claimed to have bad experiences with the Handl company. I don't have any experience with either company, but I think i'm going to wait until both lowers are released, so I can make an informed decision.