First, I'd like to say I love this idea and have always been jealous of the 'one plate' States. However, I don't think it will take the bean counters long to shoot this idea down.
None of the top ranking vanity plate States are 'one plate' States.
Virginia has the highest percentage of vanity plates in the nation (16%).
There are 7.5 million registered vehicles in Virginia.
7.5 mil X .16 = 1.2 mil vanity plate vehicles
1.2 mil X $25 = $30,000,000 revenue from vanity plates
If requests for vanity plates drop by just 8% (2.3 mil savings / $30 mil rev) then this change will cost the State revenue.
But, we can still hope.