Good point. In Denmark on their Copenhagen - Helsingor locals it seems the middle car (of three) is almost all fold up seats along the sides. Ideal for cycles, prams, & bulky luggage. However, upon observation, some Danes can be be as daft as us by cramming themselves & their associated chattels into an already busy first car when the middle was almost empty.
This is the Øresundståg service run jointly by DSB and First, that operates along the Kystbanen from Helsingør, through the Copenhagen City Tunnel, to the airport, and through Malmö C onwards to destinations in Scania (and Gothenburg when the track works...) It has to cater to a number of different journey types, lots of luggage, and does so with very mixed levels of success.
It's the middle section (so about half) of the middle carriage of each 3-car unit that has low-level access, and allows heavy luggage, prams and bikes at all times of day. It works pretty well, usually, and the trains only really get packed when there's disruption (which is annoyingly frequent).
The annoying thing about these trains is that the outer cars only have one set of doors, 1/3 along from the outside. So when it gets busy, that's why the vestibules get crowded - and this is a particular pain if it's been a busy load taken on at the airport.
In addition, the Copenhagen commuter trains (S-tog) accept bikes for free at all times (only restriction is at Nørreport station). Every line has a half-carriage dedicated to bike storage on one side, and the busier lines have now introduced an entire additional carriage (painted in rainbow colours) with the same bike storage.
But this is easy to do when you've got good capacity, and a fairly small urban population. Copenhagen has a population of only half a million (1.2 for the greater urban area) and Malmö 300k.