Based on my "newbie" status, I suggest you make your designs modular. For example, for most people with a cat 1 hitch, you could design a standard 3-point hitch connect with a short trailing piece for attaching the other implements in your line. This reduces your cost since you have a single design for the hookup and buyers can custom order the specific component they need. I have one acre of land with half planted in trees (pecans, peach, apricot, pear, etc.). I have a disc plow, box scraper, and FEL. I need a moldboard plow for the garden and a rototiller. The accessories I have are generic, which means some of the hook-ups don't always work very well. Example, the person I bought the tractor from (CaseIH DX24e) had the accessories assembled by the dealership. Both the box and disc setup have the spindles mounted on the inside instead of the outside. The support arms on the box are not designed to be mounted on the outside of the place where the link is hooked up; this results in the link always banging the metal where it is mounted.
Good luck with your efforts. Many of us, I'm sure, try to spend no more than $500 on these accessories but many times they are priced in the $$$$.