The problem with your statement is that we don't know for sure. We haven't seen everything from design document since it's only shown three characters which are Rosalina, Robin and Duck Hunt.
I would appreciate it if you just stop making up information to suit your argument. Rosalina is more likely to be first newcomer being added to Smash 4 according to database. I could see why they added Rosalina first since they would want to to testing out technical aspect to see if 3DS and Wii U could handle Rosalina and Luma without causing the frame rate issues, etc. I felt that there is no way that Rosalina would be planned to be included right after Chrom. Also there is a text under Rosalins saying that all characters were decided fom the beginning.
If you have a source that would say otherwise then please provide it because I'm definitely not aware of it.
My hutch is telling me that Bowser Jr was also planned ever since the beginning. The problem is that we don't have any access to full design document to prove our points so best as we could is depending on information we have. I have a feeling that he was planned to be included with 7 Koopalings to contrast 8 players mode which has been planned for long time.
Well, we know there must have been some sort of design stage before the proposal documents we have because we know at some point Sakurai was going to go with Chrom, but decided he was too similar to Ike and Marth. There's a note on Robin's proposal talking about how some characters "slip through the cracks" which might be a reference to Chrom. But no direct mention of Chrom.
My guess is the leaker got bits and pieces of information over a period of time and put them together with some of his own interpretations, and we ended up with an odd mix of pre-proposal concepts, a lack of characters we know were planned right off the bat, and characters cut very late in development. Or we got the tail end of a rumor of a rumor, maybe office chatter was discussing Chrom, despite him never actually getting beyond Sakurai's mind.
It's just a weird bunch of scattered information from a bunch of different times that happens to mostly all be correct, or at least, with inconsistencies that are able to be explained. I think it was true, or at least, the source was a good source, but the information was dated or interpreted by someone, maybe even mistranslated. We know the leaker liked to make assumptions based on context clues (Shulk's trailer for example), so it doesn't seem unlikely he got a message about Chrom being planned and assumed that meant he was a sure bet. Makes me wonder if Chorus Boys were ever the actual rep, or if he just assumed they were based on them being a logical RH rep.
I do agree 8 player was planned early. It's too ingrained into the game to not be. Which is why I don't believe ICs were cut because of 8-player at all, especially since we have a clear reason given why they were cut that didn't involve 8 player, although, technically, the statement was made before 8 player was officially announced.
