The majority of the question depends on what V/Line is trying to achieve. Are they replacing the H sets on Suburban routes and short hauls which would be suited to having a High Capacity layout, or are they replacing the N sets which are for long hauls? Will they try and compromise to replace both which can only end badly?
Wifi - Wifi should be provided, but it should not be free. Telecommunications companies can provide access through their networks (similar to how Telstra Air works from payphones, you can connect, but only if you have an existing Telstra account that you pay for the service with).
Double Decker - Might be nice to consider, but probably not likely.
Layout - If replacing the H sets for suburban and short hauls, 2 double doors per side as per H sets or Siemens, seating arranged as in a Vlocity now, but with more space around doorways. If they are only running on short routes, there is less need to have onboard toilets and you could probably go down to 1 per 3 carriages.
- If replacing the N Sets, keeping a similar layout would be good. Doors seals would be better than those on the N sets, so having an airlock at the end isn't as needed. The ability to walk through carriages would be more important. Not entirely sold on the need for a food kiosk on board. Possibly you could have someone with a trolley get on part way through the journey, do a lap of the train and park it until they get to Southern Cross or a station such as Bendigo.
Trying to replace both with the one carriage design - a bloody nightmare.