Can spell speed, and skill speed be combined into singular haste stat?

[Hasrat]

Probably not that hard to do, they already replaced Accuracy on all old weapons before.

They merely swapped accuracy with a comparable stat. You are proposing reducing 2 stats into 1 stat. That just sounds like a coding clusterfuck waiting to happen, because undoubtedly the stats will remain behind the scenes.

And it's more than just the stats. UI elements for certain stages of relic progress would need redone. Zodiac books needing modified. The entire Zodiac Sphere Scroll stage would need to be reworked, because you can actually apply both speed stats to any weapon.

Be dismissive all you want, but nobody that has ever brought up this suggestion fully accounts for every change the game would need to make for it. The amount of work necessary to implement this change is not justified by whatever meager improvements it might make.