Soo, Doraemon & takopi swap places, interesting scenario.. ..... Doraemon in this case clears since he's a Nanny bot, he'd absolutely help out Shizuka with her problems, knowing that her problems are shittier Than nobita's, he'd likely accompany her once he finds out her school problems, since by that point as she's a punching bag for Marina and states that only Chappy makes her life better, well we all know how it goes once he learns of the problems that Marina and Azuma's problems, he prevents their untimely fates and raises them.....? Dunno how he'd deal with their Horrible parents tho, as he's not the type to result to murder like the original Takopii did... All doraemon does is help them out with their issues if their families are beyond help...
As for nobita... He starts his life as relatively normal, strict parents, Takeshi & Suneo Picking on him and dosent know of Shizuka's qualities by that point as he didn't have aspirations for anything.... Since he's a kid after all. Takopi's situation isn't as difficult since his goal is to make everyone happy, he may see Nobita get beaten but if he results to Murdering Takeshi, this is gonna be ugly.... It's either nobita prevents him from doing so or it's a bad end. Though takopi can at best try to pep talk nobita into putting effort on his studies and plausibly succeed..?