For instance, "intended date of leaving the UK" - if you are applying to live with your EEA spouse permanently in the UK, how can you enter this date? Yet not completing this box is not an option as you cannot move to the next page without doing so.
The way I see it is: A person must apply for a family permit from outside the UK, once in the UK, with legal permission to be there, you can simple "adjust" your status, which has to be done from withing the UK.
Now, since the family permit is only temporary simply because it is also based on the EEA first 3-months rights, it must have an "end date".
Once the EEA starts exercising his/her treaty rights or I call it getting settled (ie., becoming employed, seeking employment, etc), then you change your status from a family permit to residency card (EEA2) while the EEA applies for the registration certificate.
Therefore in theory, since the EEA has the right to be in the UK for 3 months, then so do you. But after such time if the EEA wants to stay in the UK, he/she must show that they are qualified to do so (ie., employment for instance). Then, yes, you must enter a departure date, but that does not mean that you have to leave on that date.
I guess completing the VAF5 printed form (the PDF file available from the Borders Agency website) is not an option as the website states that it must be completed online. Again, surely this must be against the spirit of the EU treaty rights regs and the requirement to facilitate and prioritise the application?
You can also write them a cover letter if you have something that you would like to add or explain. You have nothing to loose by doing that. Just peace of mind.