I'd be down for what you're describing.
A weekend smash-piece relationship can still be monogamous
Like you, I'd like to do stuff (both sexually and non-sexually) when there's time for it (as opposed to a girlfriend my age/younger, who would want to be with me every second I'm not at work)
One piece of advice I have: Even if what I'm about to describe isn't
exactly what you want, it might be worth a shot while you're holding out for what you really want. I'd recommend possibly finding an older married woman who's looking for a young guy to commit adultery with. I had one of those charades with a middle-aged broad when I was 23. Since she was married (and had kids), it's not like we could be together every single second (which is why such a relationship might work for you)