My guess is that ground rules and pacing a relationship would be a great way to overcome the fear of an insane bitch (can I say that here?) playing games. What do you think?...any other good ideas?
Depends a great deal on what you mean by ground rules and pacing. The most common difficulty I hear poly/open couples around me having is the constant going to and fro between what one partner is and is not comfortable with. This can frustrate potential OSOs out pretty quickly, and create resentment between the original couple.
Yes, people cannot always (often) predict beforehand what something will feel like. But we should not allow our emotions to ride all over us and the future we are trying to create. If you are having a rough day, commit to the future you have seen before you and wanted to pursue, not to the present and fleeting state of mind that is telling you to rein in your partner and put artificial boundaries on the natural progression of their other relationships.
It is exactly as likely that they will meet someone new and run away with them even if you were strictly monogamous. In fact, some might argue it's less likely they will balk in poly because the whole 'you have to choose one or the other' pressure is gone.
As to your specific concern; are you sure some of your fear of him getting hurt is not just jealousy in disguise? In the good old "no one is good enough for my son/daughter (but me) because no one will understand what a rare gem they are (except I)" manner, but only with a poly twist.
If you feel you need ground rules, try making ones that are specific and have a timeline. "Don't do anything that could jeopardize our primary connection" is a bad rule, because practically anything can fall under that. "When we are both ready, you can have as much freedom as you want" is another bad one, because there is no timeline - there might never become a time when both are ready. "I'm afraid that if you start a new relationship, you will get swept up in NRE and start neglecting our relationship and me. So I would appreciate it if in the beginning you would just go on dates and not stay over for days at a time before I have a chance to meet them and we can all discuss what we want and expect out of this" is a good rule/boundary; it's very specific and limited in its duration.
IMO only you either give the other person their freedom or you don't. That includes the freedom to meet, fall in love and form relationships with people who wouldn't be your first choice of metamours. Problems arise when you think of abstract situations which you wouldn't be okay with as opposed to equally abstract situations you think you can handle, without having no actual experience with either. Then when reality doesn't match your fantasies, you have a situation where one partner is continously changing their mind about what is okay and what isn't, one day sulking and demanding that old boundaries that have been lifted by mutual consent be re-introduced, the other over-enthusiastic and asking they get rid of all boundaries alltogether, including the ones they only yesterday thought they couldn't do without.
(I might not always think Vanilla's mother treats her in the best possible way. However, their relationship has such depth and history, most of which I'll never be privy to, that anything I see is only going to be a scratch on the surface. I'm also aware that I might be subtly competing with her mother over who gets to be the number one woman in her life, which is insane, because we have very different roles to play for her. Additionally, people have a tendency to bitch and moan about their near and dears much more readily than to praise them for all the good they've done. All of these contribute to how I perceive Vanilla's mother and their relationship, which is not how she experiences it most of the time.)