An arranger isn't designed to be a WS. Yes, you can SORT of get away with using it that way. Same as you CAN use a fork as a knife... It's not designed to be one, so it is hardly surprising it doesn't do the job as well or as efficiently. And try using a knife as a fork... sure, you COULD, but be prepared to cut your mouth!
If you need WS features, get a workstation. Personally, I think trying to focus on doing both is what has held up arranger development the last ten years or more. There is so much that needs to be added to the arranger, and none of it has anything to do with using it as a WS. And, in the days of VSTis, computers cheap and powerful enough to do entire production in the box, why do we still get this 'me too' clamoring for stuff that WS's do? When computers do it so much better?
I'll tell you what computers CAN'T do... They suck at being a great live arranger without a prohibitive amount of work. So, let's just let the arranger be an ARRANGER...

