Latest version of cocos2d from here can't be compiled too(for Mac target of course like SB target for Mac too), so what? It's easy to fix and it's not an argument at all. Actually I pulled this fix https://github.com/cocos2d/cocos2d-objc/pull/1353 and it's applied to cocos2d classes only, but not SB code.
I do not understand what you're driving it, because I use SB for a long time and I do not see any problems that prevent me from making games. So give as an examples? Like when you developed some game with SB and got some big or not trouble?
In fact, there is almost completed the development of migration tool in SB, so you can update your project from SB 1.4 to latest SB 2.0 version. But yes, it's not completed, now it's whatever, because...:
Look around, almost nobody uses cocos2d-iphone, everybody moving to cocos2d-x or Unity. I do not consider the people who have started a long time to make their game using cocos2d-spritebuilder and now they want to finish it or simply to maintain it. Like iOS 9.x fixes or some update to the game.
So you talking about compatibility for a very small number of people who using SB 1.4 and 3.4.9, so this make no sense now.
Also, without SpriteBuilder using of cocos2d becomes awkward. Especially for those people who have already used it as I like. When I'm with impressive simplicity and in a very short time created a GUI interface, then if someone ask me if I want to return to manual creation? No way.
About what exactly things you are talking? What needs to be removed?
Maybe you wan to say iPhone 6? Because iPhone 6+ is 2208x1242.
I'm not see a very urgent task to do that. But with some fixes for iPhone 6 described here(don't forget to fix to CCFileUtils) I get great support for iPhone 6 and 6+.
The main idea is that the game should trying to look the same on all iOS devices. As I think the main issue in 3.4 is that it's using 2x on iPhone 6, but I'm using 4x on it (because hardware is the same, but you still can use 2x, but anyway it's needs to be fixed like that: bounds.size.height/568.0; also for iPhone 6+ this fix needed too) and so I got what I need(background image size 1536x2272px):
Without this fix game will looks like that: iPhone 6 and iPhone 6+ (background image size 1536x2272px ):
Also, with just simple fix to "bounds.size.height/568.0;" you can use 2x on iPhone 6, but it will do upscaling from iPhone 5, this maybe will not be noticeable, but because of hardware of these devices(iPhone 6 and 6+) are the same I decided to use 4x on iPhone 6. And looks great overall.
P.s. do not forget to set appropriate Launch Image for iPhone 6 and 6+.