Of course, when it comes to law, or any other profession that deals with such complexity, the reality of "venture of one" runs into the need for training, skill building, mentorship, etc. Richard Susskind has argued that this is one of the remaining sources of legitimacy for traditional, large law firms--they act as a sort of "teaching hospital," taking young attorneys under their wing and gradually training them in the art and science of the law. Another traditional approach is for junior attorneys to start off working as a public defender or district attorney, and then after they have a fair amount of trial experience under their belt they re-start in civil litigation (never mind the enormous substantive and procedural differences between the two fields--akin to the transition between surgery and psychiatry, or vice versa).
At the opposite end of the spectrum, there's always the option of being a "venture of one" in the form of a contract lawyer for large firms. In most (though, admittedly, not all) cases, this is a dead end street--
document review or repetitive drafting that employs licensed attorneys normally for no reason other than to be able to check the box of some practice of law or insurance requirement. This route tends to be devoid of mentorship or real learning, and the experience gained is rarely of much real value. (Of course, there are other arrangements, often also labeled "contract attorney," that involve much more substantive research, drafting, or advocacy, which are true independent contractor relationships rather than "temporary hire" type positions--labels can be dangerous).
Fortunately, I think there is great potential for junior attorneys to structure themselves expressly as solo practitioners, yet still reap the advantages of training, mentorship and experience to be gained in a traditional large firm setting. It's something I've written about frequently over the past few months: the Ad Hoc Firm. In a nutshell, every case should be a temporary assemblage of legal talent tailored specifically for the job at hand, and flexible to grow and contract as the legal task itself evolves. In the litigation realm, that might include the Rainmaker (the person who brings in the client), the Coach (who assembles and manages the team--often called the quarterback transactional matters, though I think "coach" is the more fitting sports analogy), the Strategist (who lays out the grand plan), the Expert (the person or people with subject matter expertise required), and then various Lieutenants (who take charge of individual tasks, from the minor research project to larger issues like discovery or trial). Of course, in all but the largest of matters one person will fill several, often all of these roles simultaneously. However, I think it's still important to view them as separate functions--regardless of whether it's just one attorney or a team of dozens spanning several continents.
How does all of this relate to the training of junior lawyers? Within the ad hoc firm, everyone is their own enterprise, and they have come together voluntarily to form a team to address a legal challenge. For the junior lawyer, that can mean offering one's services as a "Lieutenant" in a discovery matter, in dealing with a specific substantive area of the law, sitting second chair at trial, etc. The junior lawyer can also be the Coach or Rainmaker--what better way to pitch a client than to explain your intent to assemble a team of highly experienced attorneys, with a reasonably priced and highly motivated junior attorney taking up the often time-consuming task of coordination? And, unlike in a large, monolithic law firm, the junior lawyer has flexibility in balancing income, education and experience. I know many junior attorneys at large law firms that would love to be the second attorney in a civil trial, yet calcified firm business models often don't permit this as it would be impossible to bill for the attorney's time. It's a Catch-22: often you can't get the experience until you're experienced enough to justify billing for the work. A junior solo attorney, on the other hand, has the opportunity to make a very attractive pitch: essentially "let me try this case with you, and cross examine three witnesses, and I'll work for 1/3 my normal rate."
This isn't particularly revolutionary. It's common advice for junior attorneys to be told to try to get some pro bono work to build experience, or to try to attract small clients of their own and gradually build to more sophisticated matters. But this rarely does away with the Catch-22 caused by existing models of experience and billing. Interestingly, law students seem to have no problem forking over $40k a year to be lectured on the law by professors, but few licensed attorneys seem to be willing to forgo even a fraction of that income for the chance to gain truly valuable experience. This is where I think a paradigm shift is in order: the more junior attorneys conceptualize themselves as one-person enterprises, regardless of whether someone else sees them as an employee, the more they will be in a position to demand (or create for themselves) the kind of experience they need and desire.
As a bit of an afterthought, it's also worth noting that clients will be increasingly unwilling to subsidize the highly inefficient training models of large law firms--especially the kind of sophisticated clients with sophisticated matters that attorneys hope to work on. The very Catch-22 that prevents junior associates from getting the kind of experience they need (because clients don't want to pay inflated large firm billing rates for the associate to learn on the job) forces clients to pay for the high rates of more seasoned attorneys. An ad hoc firm, however, that provides an appropriate mix of high-paid and seasoned attorneys with much lower paid apprentices will enjoy a significant competitive advantage when pitching work.