Great Answer Ryan, I'm new to SEOmoz so this was the first one I've ever really dived into 
My feelings are very similar on this topic. I can appreciate you fighting for your client each month, earning that business, creating that value. I do use contracts though which have a hybrid and custom structure for each individual client. As every client is different so are their needs, deliverables, efforts on the part of the SEO, time constraints, etc. I currently have 4 different clients all with contractual variations of profit share, % of sales, deposit up front, increased % of consultant fee through the 1st quarter vs. the latter, and on and on for every variation there is always another way to accommodate the client.
That approach may not suit the needs of creating a service to the masses but I have more of a passion for the more personal side of business and really understanding my client's needs and goals; services less clients paying me hire margins creates less head ache and more rewarding work.
I have had a client where many contractual variations have been necessary to accommodate both ends. This has been one in which equity shares have been discussed in return for my services. Now here's where things get really sticky because I have no interest in owning a portion of this clients website because at the end of the day 20% of nothing is nothing, what I did in this case was structure a 20% profit share for my business consulting services with the OPTION to accept equity % after specific milestones have been achieved, including offers coming in to purchase the company.
In addition to this there was a price point for my services for the first 3 months that is more per month than the remaining 9 in the year. THEN we agreed to half of that 1st 3 months fee would be paid as soon as my Professional Services Benchmarks are presented. If the prospect that is in my eyes already a client, decides to walk away then yes I'm SOL at that point but in the end it's never been for nothing. Rarely, do I not earn the client’s business so late in the game, so for me personally it's worth the effort; researching, analyzing and then educated the prospect. Either way neither of us walk away empty-handed.
In summary, I am a big advocate to being completely flexible to what the client wants so long as we are both happy with the proposed solution(s), process and outcome. It may seem to many that this approach is overly complicated and too vague to be effective but when comparing this due diligence to that of an unhappy/unhealthy business relationship, you have to ask yourself which situation would you rather have on your hands.
