Almost by definiton labour is external, and not enjoyable - a "labour" is often a trial or a tribulation. While labour is essential to a society, there are certain forms that are unenjoyable to everyone: hence an incentive is needed for it.
I am still unclear on how you believe labour can be made an internal part of an individual. How do you make labour a necessity to the individual? It relies on man having a feeling of belonging and essential committment to his/her society. This, of course, is problematic and hard to achieve. Most humans are really selfish when it comes down to it - people will die for a cause and do sacrifices/things for others, but this latter condradiction is generally supplementary to the former.
Brave New World has a like situation, in the creation of different castes of people - each suited to a specific form of work, but in reality this cannot be achieved. It is true that the poor/uneducated are often, through circumstances, forced into positions such as these - but at least they get paid , they get something in return. Having people working for society's good or for something else which somehow makes it an internal necessity still won't make them want/revel in working that job, because by nature it is still a bad job which doesn't want to be done - altruism and duty to society only goes so far.
So in a communism system, then, how will people be gotten to work these jobs? They won't flock to them for the good of mankind - for that is against their self serving natures. They would have to be forced into it. But unlike capitalism, they would get fuck all.
If i decide to take Marx's famous quote about abilities and needs, then all we are presented with is an alternate form of slavery. For true equality and freedom cannot be achieved - for example, as communists get richer, they become less committed to their ideology. Avarice is a common trait - it cannot be destroyed even by force. The operation of communism is impossible whilst this exists. Forcibly removing a trait like this from mankind cannot be done. If a proletariat rebels, i doubt they are going to take (materially/fiscally) from the bourgeios what is needed to make everyone materially equal and just stop at that. Neither would a government. Their own greed would commit them to take as much wealth as possible, and establish themselves as a new represive class.
It is irrational, illogical and useless to atttempt the achievement of an ideology that requires a change in human nature: if you read literature from the earliest parts of history to our contemporary, you will find that people have changed little. To change human nature is not really possible, making any such ideology, including Marxism, a chimera. It cannot be achieved in a pure form, so it is pointless to promote it or lament its inevitable failure.
Give me one Communism nation in the world that: a), is truly "marxist" (in all or most operations) and b), that hasn't become an oppresive oligarchy.