They need an API and allow trading from non mobile devices. Ideally, they should offer extremely cost effective co-location to their matching engine, either a dedicated server or a VM. If they are just routing orders to other people, then fine but still need an API. The API also has to be of the highest integrity - one player doesn't get to jump the order queue over another no matter what. Time priority period. No fractional pennies.
They should then expand to more models. Free commission like now, and in addition, commission but all the perks. In that case, it has a great chance to succeed assuming they don't screw people over. They should be very explicit in their website about how orders get routed. For example, if the orders are mostly internalized, they should say that. Transparency and honesty should be their highest ideal.
Otherwise, it is gimmicky. It might still work, but won't get any real flight until they truly try to empower the little guy, investor or trader, to live up to their name.