There's definitely an opportunity to disrupt in this segment, although focusing on power is going to substantially limit your market appeal. For example, I'm a record holding cyclist and I've never trained power.
Yes, I'm aware focusing on power data limits my potential audience, but I don't yet regret doing it. 1) There are enough power meter using cyclists around to make this viable. 2) I'm not sure how to make this amazing for non-power meter using cyclists. 3) Strava is fantastic for more casual cyclists (not that that describes you). 4) I'm sure power meters will become cheaper and more popular over time.
You know how you can make it amazing for power meter and non-power meter users alike? Add a feature to help analyze tests. Help guide users to picking an appropriate time interval and course, and help interpret the results, and save those results to a profile.
And as power meters become cheaper and more popular, more people will be looking for ways to interpret that data. Some will turn to Hunter and Coggan's book or to a coach, but some will inevitably turn to sites such as yours for guidance. You already seem to have started down that path, but the more you can do to guide and educate inexperienced power meter users, the better you'll do.
Let me think about some ideas for #2, re: #1 and #4, I only know of maybe 5 cyclists in all my circles of cycling mates that use power (out of probably hundreds) and power meters always cost $2k every year the same way a great bike always costs $10k every year. :-)
oh, and regarding #3 - strava is good fun and bragging rights and mostly useless for any training purposes. If I understand your purpose correctly, you are really targeting a training segment, not a riding segment so Strava probably isn't a serious concern (until they decide to get into offering training features...)
