Those are configurations. It's not like they are fixed or that trains are being bought specifically to operate that way forever. There different configurations are meant to give VIA flexibility matching demand on a given segment. For example, the short configs are going to be really useful out of the Kingston hub and for Corridor West. They'll be able to keep up frequencies by using shorter trains.
That requires funding, especially for a lot of the regional rail proposals. Lest we forget that VIA Rail is a $700M agency that takes in about ~$300M in subsidies. This is absolute peanuts. There's transit agencies that get more in subsidies than VIA's entire budget. The TTC, for example, is verging on nearly $800M in operating subsidies. Metrolinx takes in almost $150M annually. So there's literally no way to add new services unless the feds and provinces up the subsidy or if savings can be found elsewhere (possible with HFR).