That's impossible.
It's too obvious.
It can't be done.
Why? The computer says
NO.
But seriously: the team at AFPEx are technically very good (I've met some of them) but ISTM that the major software is bought-in, and IMHO there is nil chance of anybody there being able to make the required financial case for spending (probably) 6 digits on software development.
You could achieve what you want (as you of course know, given your job) by setting up a web (or whatever) gateway on some IP, and having a bit of software running on that which interacts with a real AFPEx application, sufficiently to file a flight plan and maybe (for strip flyers) to also file the DEP message, but then somebody will want to support the cancel message, then somebody will want to support the free text, and then.........
Anyway, I know somebody who could knock up a simple proxy like that for a few k. It would prob99 be in breach of the AFPEx Ts & Cs though.
You could even file it via an SMS message. The protocol between the phone and the server is up to you, of course.
My guess is that EuroFPL would be the people to talk to about this kind of thing.
That is, after somebody has solved the issue of VFR addressing; which could be awfully fiddly if done manually on a phone. This could be done by the phone app, by walking the filed route and picking off the FIRs, then applying the special cases. Not completely trivial but possible.
Nobody is going to do this for free though.