If someone is feeling nesty, they'll lay eggs wherever they thinks is best and there isn't much you can really do to prevent it. If you do not want the hassles of eggs hatching into chicks, buy some fake eggs and switch out the real for the fake. Not caique, but when I'd got tiels (2 males purchased, 1 female adopted after being dumped) I didn't own a nestbox so the tiels improvised. I had a paper supermarket bag on the floor between cages w/some foraging items in it - straw fingertraps, stuff like that. The tiels formed a pair, chewed up the chewables, laid eggs and sat on them.
Don't battle, as you put it, what comes naturally. If they want to get happy, they will. Then again you might get a companion and the two may hate each other. You can't tell any more than you can with matching people. Disrupting things in their life like rearranging toys, putting in new one or moving the cage will inhibit nesting but won't necessarily stop it. If they feel secure and safe, it might lead to nesting and vice versa. One thing to note is that whenever you think you've finally figured out how to avoid nesting the birds will fool you. One of our members removed all nesting stuff but her tiels still found a dark hidden spot to nest, lay & hatch in.