That's totally fine, I'm not suggesting you do need to start solids now
Just that by the time he is firmly on two naps and through the transition it may be something you are thinking about and wanted to give you an idea of how that would work.
Was unsure if offering more milk at 3 hour mark would revert him to a newborn routine and also create an association / prop with going to sleep and cause issues at night but if I leave enough time for quiet activity before nap /BT then it shouldn't be an issue I guess.
What is EBT?
Well in some ways, yes it is a bit more like a newborn routine but honestly I can't see an alternative - if he can't manage to get through A time plus nap on just one feed, you do have to add another in somewhere and I would suggest around 30 mins before nap is a good time to do so. It doesn't have to be another full feed so more like a 'snack' to get him through the nap without hunger waking him. Unless he is actually feeding to sleep it shouldn't cause issues. EBT = early bedtime