Seems to me if you know you'll miss your flight in the last 15 minutes (ie: not at the airport, have a meeting overrun) a quick call to QF will solve the issue just move the flight to another later one. I don't know this will have a massive impact on a lot of people, but then again I don't purchase these sorts of fares
I don't know it's a real issue re L,V buckets. I did notice LFLEX fare show up in a fare list the other day which i found interesting, as I'd never seen the L bucket used before for FlexiSaver, but maybe that's just me not noticing

Either way, if you purchase a Flex(i Saver) fare on qf.com before/after the changeover you'll still earn at the appropriate rate.
the kicker is for non-QF channels (eg: OTA's and shop front TA's) who may think oh V is still flex, but then again i do suspect this will really affrect a small number of people and even less who would care for things like SC's etc. At any rate when making a booking the conditions for that fare type, at the time of booking, will display and show and that's the guide. I'm a nerd so I usually read at least in short form the fare conditions to know what I'm in for if it's a new fare for me or I am concerned re changes or the like. I know a lot of people don't of course
my 2 cents.