While I cannot comment on any changes in the National program in the past few weeks I can tell you what a National corp rep told our company about the EA program. The decision to put cars besides full size and Intermediate on the aisle is up to the local manager and is normally based on car availablity. For example if they have a lot of non - EA full size reservations they might be more likely to put luxury and other cars on the aisle. However, the EA program is mainly marketed to business travelers and the majority of business travelers, including myself, will pitch a fit if faced with driving a mini van!
The majority of upgrades you get for free with coupons and other things (EA, Credit Cards etc.) are up to a full size car. Most rental car companies will not upgrade you to a luxury, SUV or mini van. These are high dollar cars for them. They charge a premium to rent them and make a lot of profit.
As has been said before time and time again. Do not use the EA program if you must have a mini van. For my 9/22 rental I had a choice of SUVs, but no vans!