yes

Yes it allows for higher resolution with more or more powerfull ram. See ps4 

Rendering higher resolutions mainly comes down to the GPU these days ... 

A GTX 980 Ti has less memory than the PS4 yet it can render games in 4K whereas the PS4 can't even do 4K for AAA games ...

Nope. If I wanted a gaming PC I'd use one. The whole reason I use consoles is because I prefer, as somebody who majors in the CS field, to keep computers as work and keep them separate from play.

Definitely not. If you want to be able to upgrade, just buy a PC.

Nah, that's what gaming PCs are for.

No. The strength of console gaming is one basic spec games are made for.

Besides adding more RAM just places the bottleneck somewhere else, even replacing the HDD with a fast SSD drive only has small benefits.

And realistically how would you upgrade the RAM? It's all soldered to the board, making it modular and upgradable would add a lot to the cost. Connecting it to an external port would be pretty pointless.

I think this would only make sense if games were still required to run with the basic amount of RAM that the console ships with.

And I guess it could introduce certain theoretical security problems, as it would be an interface to the core system that could be messed around with by hackers.

This really split the N64 market back in the day. Some games were unplayable without the memory expansion.

Look at the Nintendo 64 and the Super NES, that's the base model for this kind of scenario.

We need to see a return to cartridges for this kind of stiff to be viable, and even then, downloading more RAM is expensive.