Regarding alternative delivery methods, see the thread:
"DIY easy high dose anti-oxidant therapy" started by moondaughter,
Moondaughter provides a link to a video which shows how to create tiny liquid droplets with an oil skin (liposomal encapsulation) using an ultrasonic cleaner (cost about $30). These can get things across the BBB that would normally be blocked.
In the thread, I describe my experiences with dopamine (or, rather, my proxy for it: banana): some benefits, but the lack of a pure dopamine source meant that I had to take large quantities of the liposomal preparation, leading to feeling nauseous, and the worry that toxins in the banana would get through the BBB.
Pure levodopa should be possible to encapsualate.
It would probably be undesirable to encapsulate carbidopa. This is because its property of reducing the conversion of levodopa to dopamine, is only desirable outside of the brain. Inside the brain, we want the levodopa to convert to dopamine. Thus, we require that the carbidopa does not get into the brain. This is the case, ordinarily, because it cannot cross the BBB.