Would I be very mistaken in assuming most of your experience is in embedded systems?
Yes. Stuff that has to work, with more or less zero bugs. Z80, Z8, Z180, Z280, 80x86, H8, AVR. A good compiler generates the same code for pointers as for explicit arrays, and the latter is far more solid.
There are quite a few "technology types" in GA, and lots of them are software developers. It's tempting to wonder what could be done better and no doubt this is what has resulted in super sites like Drauk's. Myself, I have looked into various avionics products but a quick analysis shows the difficulty of flogging something into this market.
Which is not to say it can't be done, but I don't think I would try a comprehensive online flight planner, on likely subscription volumes alone. Look at Avbrief - they have not (apparently) improved their product for years, and have gone on the record (in another forum) saying they make more money from a few airline customers than from the whole of UK GA.
There is another issue with an online flight planner: the cost of the bandwidth. On PAYG GPRS/3G this is typically £10/MB when abroad and this rapidly becomes quite significant. I did try JIFP briefly and reckoned on spending £5-£10 on a quick flight planning session. One can't use an internet cafe PC because the application (Flitestar, basically) has to be installed locally. The only cheap way is to have the app installed on a laptop and connect over wifi or an ethernet cable. But even wifi is getting pricey now, with almost every hotel charging for it by the hour. And most pilots do not have mobile internet access - judging from how many never look at notams
So I don't think an online planner would reach a broad audience.
LH2 - the Eurocontrol site contains various report generation features, and while these are PDFs they can be machine parsed.
One checknut is that
AFAIK there is nowhere to get CAS shape coordinates. DAFIF used to have these; machine readable, but now there are just the national AIPs which have to be human-processed.
If you have a commercial requirement, Eurocontrol will sell you the data. The site is run by an outfit called Frequentis and they sell various tools. I don't know any more than that, never having looked into it.