Government should relax obligation for them to be able to deliver every day to addresses, who really needs this - can that be efficiently delivered.
I wouldn't want to start paying PO a yearly delivery fee subscription like many pay to Amazon though.
just like to see a reduced postage fee for sending cards over Christmas - nice to send relations cards but the price of card+stamps adds up.
All sorts of people and there is no way to tell who and when.
As it is, at the moment if for example you get an urgent appointment from your doctor or hospital they know they should be able to contact you within a day or two at most by sending a letter, if you reduce the delivery days that goes to 3-5 with ease (they might be able to ring you with your new appointment, but many people don't think to update their phone number when they change it).
If you start to say "yeah you only need to deliver 3 days a week", or similar you hit the point where all sorts of companies, and government departments will need to start spending far more on deliveries as they'll have to use things like couriers who are both more expensive and far worse for the environment.
On the plus side think of all those courier driver jobs, and profits to the courier companies.
You would also likely need to significantly increase the size of pretty much every RM depot and delivery office in order to allow them the space to efficiently hold several times as much post as a matter of routine than they do now as many of the DO's are probably closer to capacity than they were 30 years ago due to things like increases in the size of the towns they serve, and the number of packages being delivered, and then probably have additional staff as they're more likely to deliver to a higher percentage of houses on each round, meaning you need to rework all the calcuations on the size of the rounds* and how long on average it takes.
*IIRC they already increased by a third a while back, and there was a big issue with the way they were calculated, from memory they used a software programme that didn't allow for things like the time taken to go down garden paths, open gates, or wait for people to open doors, and IIRC for vans it was done without taking into account week day traffic.