On the one million point system:
I don't think score will ever be something people compare much among each other, even with ScoreV2.
Just imagine someone saying "Look at this play on >beatmap< I got a score of 900,000!"
I think people will still go off star rating, pp, combobreaks, accuracy and of course, the selected mods.
It's too hard to encompass all these into just score and difficulty of the map, and it just feels less rewarding when score is changed to become generally much lower, while it feels like cheating, almost, when you play a short, easy map, and get over a million score. Also, for instance, a doubletime 800,000 score might still be much more impressive than a nomod 900,000, so just score alone won't do.
On slider accuracy:
I think it's too big a change to implement. Slider leniency has its downsides, in having sliders feel lackluster in terms of acc'ing them, but at the same time, it's the system that allows for many types of maps and things to be playable and rankable. For instance, when you have a sudden, unpredictable shift in the music, or a very slow part, it can be very frustrating with hitcircles given the difficulty of timing, without much of it actually being your fault (to your feeling, at least)
And that's without mention of dubstep and similar maps. They'd take a HUGE hit from this new slider accuracy.
Even so, when I was relatively newer, I did think "why can't sliders have accuracy?" After all, it is a rhythm game, and I myself am generally pretty good at getting good accuracy. But after playing a LOT of maps of all different types, I see it as a positive thing. To remove it seems like pandering to generic, anime mapping, which has enough going for it already.
Anyhow. If scoreV2 was implemented, the entire pp system should probably be overhauled as well... It has some rough edges, as well as probably getting broken by slider accuracy.