i like that you are asking these questions, and that you are considering the other person's POV in this. especially as someone who has been on the other side of this issue, looking for equitable work trades and
land share agreements with people and finding instead a lot of exploitation disguised. well i have had some good situations too, but the majority of bad situations, the drama and power trips and BS just outweigh the positive experiences i have had. so here's my two cents....
to me it sounds like you are looking for more of a land share situation than a woofer or a work trader. i suppose the words arent that important, what you call it doesnt matter, but it sounds like you are looking for someone who is willing to invest more and therefore hopefully get more out of the deal than a woofer or a work trader. maybe though actually you would be looking for both, someone who is lightly invested as a work trader, someone who is more long term, looking to invest in a place.
someone with a lot more or equal, experience and knowledge than you have, and not to train someone, a self starter. i think that someone who has the level of skill needed would be looking for more than just a spare room and food provided. imo the things that would attract that more experienced person have a lot to do with intangible things, things such as having a lot of autonomy, private space and a space where they can be independant.... and ability to call their own shots, not be so much under your thumb and always having to do things in your way.
would you consider carving out a small bit of your land to give in exchange for the work? obviously i dont know if you can legally do this, or would desire to do this. if you were, i think this would be attractive to the sort of person you would want to attract. even if it is just done in a way that for your mutual understanding that section was theirs to do as they please (within obvious limits of
common sense and etc) and there was some kind of written agreement to express that understanding, without a legal subdivision. the most attractive would be to offer an actual deed of a smaller portion of your land, in exchange for the required work for however many years. obviously you would want to try out this situation with someone before committing.
something i have heard of people doing is to compensate people by having so much time, at a specific rate to be worked out (in writing ideally), at the completion of a project to enjoy it. for instance someone builds a small cabin and then after it is complete enjoys a couple of years with no obligation to work as compensation. in that example it would be only fair that you would have to provide tools and materials or money to buy them. or another simple example they work for six months of the year, at 20 hours a week(or whatever is decided, again ideally in writing), and then have six months free. if space was provided for their own projects, and there was encouragement for the person to do their own independant projects, even with six months "off" the person would likely still be doing interesting things that improved the situation, just with their own motivation and without being monitored.
this would draw more of the sort i think you are looking for, someone who is interested in starting their own businesses or income producing gardens, building their own structure with their own tools and materials, a self starter type who doesnt have land of their own. and going into it you would have a different dynamic than that of a worker and boss, more of a partnership type relationship.not to suggest things still couldnt go wrong, but i think this is a better framework.
i also like your idea of the 80/20 split.
out here i know of several people who are looking for situations more of this sort, and who have been through different (mostly dysfunctional) situations with work trade and are basically burnt out on the idea because of negative experiences. they would go more for something like this, though, where they had a lot more say and security in the situation, or more of a business partnership where they have the will, the back, and knowledge to make a farm related business, but not the land, and someone else has the land but not the time or drive to make it happen.
it would be fabulous if people were coming up with much better models than the exploitive situations that happen, because it seems it could be quite simple and a win/win for all involved. thats what i thought when i first started with situations like this, that it seemed simple and should work, but negative experiences have made me more wary.