So quite the necro-bump here, 9 1/2 years later, but thinking about a Warforged PC and seeing what's out there on this aspect of a Warforged
So some thoughts...
Why say no? I mean, does a Warforged with romantic awareness need to NOT be a thing for a campaign to function? They were created to have awareness and freewill, insomuch that they can analyze a situation and make a choice to fit the situation. Though at least mostly built for war. I would think that with freewill they would grow into a more fully and rounded sentient mentality.
In part, the above is... anthropomorphizing a human's view of sentience. But also to me, a PC race, or for me, playing a PC race that's incapable of emotional intimacy is just boring. I realize of course not everyone is going to feel the same way. Not saying I want to play a Whoreforged, I just find it hard to think they can't eventually develop feelings along these lines, not that they'll be automatic, just that such a closed door bothers me.
Physical Functions of Intimacy? No reason they couldn't change themselves or be rebuilt for it. The real question is how they arrive at the desire of such functionality. But if/once you do arrive at this question "at the moment of truth", I'd think it's more of a non-question. If you never do arrive at this question in game though, then it's really a non-issue for that game as well.
Reproduction? I don't see why not. Probably not your usual biological reproduction, but not impossible. I mean, they aren't treants or other plant based creatures even with the wood components, but you could do it that way, and as they grow up, they add stone and metal to themselves as needed
They could also build a child, putting ideas into it, kinda like the Transformers would do when going to the interior of Cybertron and giving life to new Transformers.
And really, with magic and some hand waving, regardless of how you explain things, it could really function just the same as any other PC race's reproduction in practice.
So obviously, for a given game where a DM and players wants these things, there are ways to explain what may not seem at first obviously possible.