That's very nice to hear about the changes. I think the problem that had me with Employees Only XXX was that the puddle was difficult to jump over due to the low ceiling and puddle. Even in the regular versions of the stage it was difficult to work around the puddle since colliding with a wall while sliding still count as a slip. It was the stage I didn't like much in the beginning, and was the one stage that led to the game crash I found involving the timer acting up.
For the Arcade mode you could have it to where you're given misses ( Mostly so you don't have to type lives out, and can use X's for each miss given to read XXX when given your third one ). After reaching a certain point amount, one of your misses is removed or you gain a bonus for having no misses upon receiving the bonus. Too many misses, or you run out of time, and the game is over. That way, the player's focus is on finding out the best way to maximize time and score through serving correct drinks, finding paths to completion, and even getting some last minute drinks to take to the exit.
In my opinion I do think the obstacles being removed is good as the one thing that did bother me about the slip minigame ( which was why I preferred the simplified version ) was that having to take your hands off the arrow keys and enter a set of 3 directions in quick succession isn't so easy. I felt tapping a specific direction was a lot more manageable under the stress of losing all your drinks.
One idea I could share when looking at your idea of "finding an optimal path" through a stage, you could have a small window in the beginning where you get to run about the stage ( At least 5-10 seconds ) before the stage begins proper. Either that or a pan of the stage to get a small rundown of what to expect. This won't be available in the arcade mode, but for casual players it could be nice to study to stages for when things get serious.
( Sorry if I'm pretty much creating lists upon list of my personal ideas and the like. Having played a good amount of the game myself I'm quite excited to see how things go and stuff. As well as wanting to look forward to the rest of the development )