Non-rapacious IP agreements? - I will not promote

Looking for some thoughts on atypical IP agreements. First, yes, we're going to use a lawyer, but we want to think it through as much possible before we start that. Second, this is a bit of different situation. Yes, I know, everyone's different, a special, beautiful snowflake. But in this case, we have three experienced professionals, two technical and one with domain expertise (and some technical competence), each with their own existing professional career and business. Also, we've managed to bootstrap things, and we have our first customer. Investors aren't a major part of the picture right now, and maybe not in the foreseeable future. So far we've been bootstrapping, and there are some consulting fees, which aren't a fortune but have made this feasible (in addition to each cofounder's other income). We're not looking to become a silicon valley unicorn, here. Product-wise, this is a bit more of an enterprise-y product that runs on commodity hardware, not a phone app, or website, or a SaaS play, etc. On to the question: We've been doing consulting work for a client. Part of the client agreement is that we retain all the IP. The client is pretty happy with the results. For him, this product started as a means to an end, but he thinks there's potential to productize it. He's offering to help us with the sales process, putting us in touch with people, etc. He has credibility in saying this; he founded and ran a moderately successful software business that served a niche industry. He's semi-retired now and pursuing things that interest him, in the non-profit field. As part of that, we need to formalize this thing, form an LLC, assign the product IP to the LLC, etc. So the question is, for most startups and technology companies, the IP agreements are pretty blunt, ranging from "we own everything you think of" to, at a minimum, putting all existing product-related IP entirely in the company's name, and treating any further product-related work as a work for hire. But, as I said, we have existing careers and businesses as consultants. The intent all along was for the domain specialist to use the product for his own business, and there's some possibility for the technical founders to do some things in that direction, also. That's part of why we retained the IP. The domain specialist has done things like this in the past, working with technical people to build specialized software that he then used in his consulting work. He's a domain specialist, not a software developer, but he has some technical competence. Also obviously, we want any future work on that product to be assigned, but not unrelated work (of which we all have a fair bit). And, having been on the other end of that stick at various times in the past, I'd like to consider alternatives to the popular approach of "it's the company's property by default unless you get permission and file paperwork." Another thought is that I've been involved with a few startups that cratered, and then all the IP and all that work went into a box and never again saw the light of day. I don't want to plan to fail, but perhaps some sort of language like you hear about for movies, etc, where the rights revert after a certain period, if not used? For non-competes, again, the industry norm is typically very blunt, how do we define that reasonably narrowly? Perhaps define it as doing work for customers that you have worked for through the company, on products similar to the company's product? What other aspects might it be smart to think about?