Summoning Reactions
Yes, it is technically possible to summon creatures using reactions, I know. You define an item with a syndrome that gives someone a one-time summon interaction, put it in a reaction as the product and have a dwarf be affected by the result. But it is so convoluted. Needlessly so.
You can't use SYN_INJECTED because there are no syringes in Dwarf Fortress. You can't use SYN_CONTACT because the chances are, the dwarf has gloves or mittens so it doesn't touches their skin. Someone actually needs to eat the damn thing if you go by SYN_INGEST route, which only happens if they are hungry, so a random dwarf eats it. SYN_INHALED is fickle as they may affect anyone around.
I mean, it is very much possible to summon creatures through interactions. Why not have the option to craft? To summon things with a reaction, like a summoning circle thing. Dwarf puts down a bunch'o stuff on a workshop, workshops, and a creature comes out. No syndromes. No randomness. No bullshit.
A [NONEEDS] Tag
Creatures with the tag [NOEMOTION], such as intelligent undead cannot fullfil their mental needs and eventually become completely unfocused. I don't think this is intended behavior at all, so why not a [NONEEDS] tag that nullifies any need progression? It would line well with the general vibe intelligent undead; a stagnant, dead, soulless creature stuck in time.
Pet assignment
I had a queen in one of my forts and I wanted to give her a pet unicorn as a personal possession. It can't be done though. There is nothing wrong with allowing random adoptions, but the player should be able to give people pets as they wish, at least to nobles, since we can give those items.