A couple of comments:

Viability of solutions - When coming up with a solution, the solution should, ideally, be one that can be applied very well to the existing market, without having to reformulate large portions of it. For example, we couldn't use a "tangible product" distribution method for current e-goods. The current market is not structured to sell "tangible products" and virtually nothing in the category of products we're talking about is distributed tangibly. (A few exceptions include high-end 3D packages requiring dongles.)

Renting Content Creation Software - I have a problem with "limited term license" (rented) software in that the content or products that I might create with it will be inaccessible to me should I fail to continue my subscription. That accessibility isn't determined by predictable events, like an OS that may be incompatible, but due to simple reconstruction of a standard economic model that creates a "captive audience" for the producer - Fail to continue your subscription and you can never access content that you created, yourself, with the product. That could be content vital to your business, which makes your business a "captive audience" to a third-party, who can raise their price whenever they wish.

Here's a possible solution: Login authentication and encrypted content.

The way this would work is fairly simple, but requires a new content scheme in the base software. Content would be installed using the software, itself. It would be stored on the user's machine in an encrypted form and would be decrypted upon loading into the workspace. (This already takes place, so it's not a novel mechanism.) In order to install a product from a distributor, the user would purchase it as normal, online, then use their software to contact the server of the distributor. They would upload their purchase and authentication code (one long alphanumeric number) and the product would be transmitted, in an encrypted form, and installed to the content directories in an second, filtered, encrypted form, creating a user signature associated with that encrypted content in the process. Unencrypted content could also be transmitted as well, like UV maps, readme files or for merchant resource packs and the like. A central server for login authentication is not necessary because this scheme would require the distributor to register with the program's publishers. Upon registration and a nominal fee, the disributor would receive their own distributor key, which enables the generation of product keys using a proprietary key generator. Basically, DAZ3D and Smith Micro. Distributors would get their own signature key that is compatible with the software, providing traceability, and would get the ability to generate their own keys for their products. Not only would every distributed product have traceability in that its keys are dependent upon a distributor's key signature (which would be partially included) but, upon installation, the file is further encrypted/built using the user's own license key for the software.

In essence, a program like Poser would be able to decrypt these files on the fly, much like it does with .obz files. (Proprietary format, not really encrypted, but used for example.) But, because the files are specifically encrypted... very well encrypted.. they would be useless to anyone without the key and the authenticated software that encrypted them - The purchaser's own licensed copy of the software (A registered copy of Poser, for instance.) used to recrypt them into its content directories. Also, installing them would be difficult, since any installation would have to decrypt them and interface with the program in order to install them. (Internally, the program could keep a verified list of verified content.)

Foolproof? No. Nothing is foolproof encryption in the electronic world. At least, not yet. (But, it's getting closer to being a reality. An expensive reality, but reality nonetheless.) However, one thing this does do is help to provide the foundation for the publishers and distributors to form a working arrangement with each other in order to safeguard the market that they all depend upon. It also doesn't significantly alter the current distribution scheme. But, it does require cooperation between software manufacturers in this market. (Smith Micro and DAZ3D) At worst, even if they didn't cooperate, but chose to use this scheme, distributors/resellers for this sort of content would simply have to pay two license fees in order to acquire key signatures in order to distribute encrypted content. And, if they didn't want to pay that fee or be "married" to distributing encrypted content? They would simply continue distributing the content as they do, today. Though, I'd warn that if the publishers decided to use this scheme, they'd likely phase out accepting current formats, eventually.