I just re-read the vol 28(when mitsuhiko and ai were lost in the forrest),and it confirms what i said before... i still have a problem with this potential couple,cause i don't think haibara shows much interest in Mitsuhiko(most of the time she uses him) and when she was aware that he had a crush on her,she seems a bit sceptical ...
and even the moment when she told him that he shouldn't be intimidated by Conan,it was more for encourage him and make him being more mature,(for me it's the same thing as when she said to the DB to not rely on Conan,or to not trust appearences...)
morover when she complained about being an animal lover,it seems like Mitsuhiko was a bit desappointed by her attitude,he took conscience that she wasn't exactly like he discribes her,and then he turns to Ayumi,the other girl,who shares the same opinions as him:
you can notice haibara was happy to see that he turns to ayumi and started to have a crush on ayumi too....(so i don't think you can take the crush of mitsuhiko too seriously,since he always put haibara and ayumi on the same level

)
i think it will be always like that,haibara likes DB a lot ,but she always wants to put a distance between the kids and her,because she's not like them,they will always consider them as kids(even if they grow up together,there will be a disparity between haibara and the DB,due to her age,her experiences...,she won't consider them equal to her)
to my mind,gosho introduced mitsuhiko's crush on haibara,to make her situation more similar to conan's situation(ayumi in love with conan

,so that she also have a kid who admires her... it's gosho's style after all...
and you are all assuming that she will stay as a child?what sort of lesson did she learnt if she choose the easier solution,instead of facing her destiny,and her futur life? she should stay as a child to keep a good deguise in case some BO member would stay in freedom,after the final showdown?and she should forget her identity,her past life just because she had a very hard life?akemi and her parents made part of shiho's life,so i tink it would be a waste if she stay as a child,it would be very contradictory to the values she learnt...
remember what she said about people who goes against the time,they're always punished...(vol 19)
She can return to shiho , stay in agasa's house and having contacts with the DB as a big sister... anyway,that's what i want ;D