A normal, non-exit relay node will not be identified as "trafficking in illegal bits" by any sane police force. A normal relay will trade from A to B in only encrypted traffic and will not touch websites on the behalf of users, only other relays.
It is rare that an exit node is raided but there has been no known occurrence in which a normal relay was raided.. nor would it make any sense for there to be. Many people run non-exit relays as they are uncomfortable with the risk of exiting for the Tor network, perhaps you should be one of them.
I'll throw in another anonymity network (I2P). Its design is similar to Tor, created in 2003 and is mostly interesting due to some of its properties (tunnel based/garlic routing, everybody-is-a-router, etc).
Running a relay to help could be a good start. It's pretty simple[0][1]. The risks associated with being a Tor exit node do not apply to all relay types and the network can be helped greatly by running a standard relay too (standard relays only pass encrypted traffic from A to B).
It does not hurt any nodes used for the connection's anonymity, it does hurt their connectivity and performance. Tor nodes are publicly known and are not the same as Tor users. One of the many problems of BitTorrent or any high bandwidth application over Tor is the lack of capacity in the network (but there are others, as mentioned in my previous comment).
BitTorrent has to provide an IP address; it is part of the protocol. The issue is that some, most clients even if configured to use Tor will leak the true IP address of the user and not use a Tor exit's IP. Not good in any case.
BitTorrent over I2P exists (and is popular). A torrent client is bundled out of the box. A custom spec exists for this also[1].
As for Tor.. Tor and BitTorrent do not mix; the bandwidth is not available (BitTorrent chokes Tor relays due to model used between them) as well as the amount of data which can be pushed overall. For the most part (though this would not be relevant to a formal BitTorrent over Tor design), BitTorrent is not anonymous as most intend over Tor[2].
As I understand, modern cryptography is distinguishable from "random". Onion and garlic routing provide more useful and productive ways of reaching the same goal.
Any cryptographic application could be vulnerable and not "hold up". It is wrong and dangerous to suggest that any program or tool is absolute. A court case in Germany not long ago involving RetroShare and its f2f nature did not end well[0].
VPNs are constantly being mentioned as a solution to companies, governments, etc attacking privacy but it's extremely easy to make a bad choice and end up with more than you bargained for (a VPN ran by someone you were trying to escape, for example).
It is still possible to do the following:
1) Wiretap the VPN.
2) Correlate with bandwidth/time.
3) Keep logs as a VPN provider.
4) Hack the VPN and do something evil (log, change content)
5) Block access to/from the VPN.
6) Correlate access logs with the VPN IP address (not always applicable, not all providers give unique IP addresses)
The VPN provider doesn't have to want to betray you to do so.
I could create "ProTurboVPN" and promise "anonymity", privacy and no logging, "nobody's touching your data!" but it won't stop the above problems.
Even if I want to save the world as a VPN provider, I might not be able and it's safer to remember that than pretend I can and in the process, get someone into trouble.
It is rare that an exit node is raided but there has been no known occurrence in which a normal relay was raided.. nor would it make any sense for there to be. Many people run non-exit relays as they are uncomfortable with the risk of exiting for the Tor network, perhaps you should be one of them.