>>39806
What a coincidence, I was thinking about the same thing today and have something very relevant to this topic.
I've seen someone cosplay as my waifu before at a con, which was fairly surprising given that I wasn't expecting it at all. Key thing being here that I saw them by complete surprise, at a distance, and with them only partially facing my direction. It's an odd feelings to say the least, since for about 5 seconds I pretty much couldn't think straight and locked up to an extent. For those 5 seconds my brain recognized the clothing and the hair, put 2 and 2 together, and thought that she was real. This is probably going to sound spergy as hell, but for those 5 seconds I wanted to drop everything, run up, and hug her (which I thankfully did not do, I just stood there dumbfounded).
Now I don't know what happened first, me seeing the cosplayer's face or reality kicking back in, but once those 5 seconds were up, that feeling of pure amazement and warmth faded away. With logic back in place, I could recognize that it wasn't here and that it was just someone dressed as her. I'm no expert on how the brain works, but I'd guess that the subconscious had something to do with that or perhaps a similar aspect of the brain. It's a combination of not expecting it and the quickness of the moment that literally tricks your brain into thinking that she was real. There's no evidence to shatter that fantasy until something about them registers wrong in your head (height is off, clothing isn't right, face isn't the same, etc.).
Pic related, one of the best cosplayers who have dressed up as my waifu, but even then she isn't her. For me, I have never and probably will never see someone cosplay her perfectly. Hair is wrong, dress materials aren't correct, face shape is wrong, height is wrong, she's not Asian (Sorry but it's true, she's a little french girl (ironically enough, Russians do the best job)), etc. There'd be so many little things to break reality for me. We're not even crossing into the acting territory either, and given that I rely partially on head canon, it'd be hard for people to mimic that as well. I don't think I'd even want to cosplay with someone dressed as her, since it'd be a reminder that I'd never be seen with the real her by my side. Someone can try to dress and act like her as much as they'd like, but they'd probably never be her.
Boring, theory/opinion based stuff below
That being said, I don't think it's possible to get the same effect when purposely going out and getting someone to cosplay as them for you. Could you trick yourself to an extent in believing them, or could they maintain the character facade so well that it's convincing? Sure, but you probably won't get the same feeling. If anything it'd have to be a complete surprise, like if someone else hired a person to do that for you. Even then your reality is going to be shattered, since they're going to drop the role at some point, or you're going to run out of cash to pay them with. Not going to lie though, I'd be interested in knowing the charge rate/amount of time someone could theoretically pay for a service like this and continuously maintain it.
Of course, there's a lot more factors that go into it as well, accuracy of their portrayal, their limits of what they'd do, the morality of getting intimate/sexual, and many other things. Let's be honest here, if someone would good pay for a convincing experience, there's going to be thoughts/desires for hand-holding, hugging, kissing, or even sex. What if they don't offer this as well? What if they refuse to touch you completely, yet try to act affectionate? And now what if this isn't the first time this person had roleplayed as someone's waifu? What if you want to "go all the way" and the person playing the part isn't as "pure" as your waifu is? All of this would really mess up a person's perception of things, and the blurring of the line between fantasy and reality would be huge.
I just think it's a bad idea mostly due to how confusing it can be in regards to both emotions and mental thought. It'd be like living a constant lie, which can grow progressively worse if you actually fall into believing the act (sure you accomplished your goal, but at what cost?).
In regards to AI they should technically fall under the same umbrella, but I'd think it'd be different if it was advanced enough. It would be something that could "maintain" the act 24/7, doesn't have any other obligations to anyone else, and can stay consistent with information given personality and such. There's lots of other things to do with it, but this post is probably big enough as it is, so I'd rather not get into it.