You just need one of those bar codes to be printed out at home, just like with airline check in (or as I reported, already available with Nederlandse Spoorwegen and presumably with DB, etc as well).
Some TOCs are currently trialling print-at-home tickets for certain routes and flows - though I think it's mostly just for advance tickets at this stage.
CrossCountry have been trying quite hard to push this and if you are booking an advance journey solely with them that's covered by print-at-home, their website will now charge you £1.00 to opt for TVM collection. Though again, you could book the
exact same ticket with another TOC or ticket reseller and get free collection.
I'm not a fan of self-print tickets, and I actively avoid them by using other ticket sellers as described above. What puts me off is the fact they're incredibly easy to make duplicate/fake copies of, and that the TOC will treat the ticket as such until I produce ID to prove I am who the ticket says I am. I realise that the same ID is required to collect orange stock from TVMs, but I don't have to produce it to anybody for inspection, and my ticket is not necessarily going to be greeted with suspicion. Oh, they also operate ticket barriers properly, too (though I understand some of East Coast's barriers now have barcode scanners, negating that point somewhat).
All trains need to be wifi'd, at least for the staff, so that both customer and staff can enjoy a good and safe transaction experience.
I think we're still a long way off that. For the most part, onboard wifi systems use the GSM networks to provide their Internet access - and anybody who's tried to use a phone on a train will know how ropey that can be outside of built-up areas. I understand the wifi on East Coast uses a dedicated trackside radio system which the trains pass data off to. I've never used it to find out if it's more reliable, but there will always be blackspots. You're unlikely to see other TOCs going down the EC route for this - it would simply be too expensive.
Simply put, if Avantix machines are going to be going online regularly, with nothing better than a wet piece of string between it and the world, it could actually make things worse than they are now for guards. With the exception of online-only cards, there's currently a fairly clear line on what can and can't be done onboard a train. If you start making them go online, and start promising things to people, they're going to start getting annoyed that a lack of mobile signal means that half the time their tickets get declined. This increases complaints to the TOCs and could put guards in a confrontational situation.
There's also the slight issue that even
with a reliable source of mobile data to the train, the card issuers aren't going to be happy about secure card data being transferred across a (potentially insecure) wifi link.