or a way faster blitter or DMA would have been nice as well 
The V9938 was indeed quite slow with blitting.
But perhaps MSX2 was a bit punching above it's weight there with having 4bpp graphics. I mean I'm no hardware guy, but I could imagine the V9938 having to run at higher clocks than it did already which I suppose would complicate things/make it possibly significantly more expensive.
Just having V9958's horizontal scrolling is perhaps more realistic, and possibly having a screen mode in between screen 4 and screen 5 to allow more 'performance-per-pixel' so to speak (something like having 4 colours per character line or some such as opposed to screen4's two colours). The jump between screen 4 and screen 5 seems to big.
And yeah I agree a better pattern mode would’ve been pretty cool as well. Very cool actually. Look at what amazing stuff people are doing with screen 4 already. With 4 colours per character it would be virtually limitless. Combined it with hardware scrolling…
Exactly! And while we're at it, a priority bit per 8x8 tile so that sprites can appear behind tiles 
Also sprites in the V9938 are a bit disappointing. In such an improved pattern mode for games, sprites could have done with 3 colours per pixels instead of just one. As a trade-off, different colours per sprite line could perhaps have been omitted if necessary.
And yeah, sprite mirroring, like Sandy Brand said would've been real nice.
If only...
Thinking about it, the V9938 was arguably quite unbalanced for gaming.
Even MSX1's TMS9918 had some strange choices. I mean, screen 1 is a bit neither here nor there; why does it even exist?
Anyway, as they say, hindsight is 20/20.
