Susan, I don't mind at all! Like I said, you're already going far beyond what I expect people to help a stranger with.
Let's see. Effects. The effects don't impact the performance that much, although I suppose they do add up. This is probably OK though, as all of them combined don't seem to produce that much of a slowdown, and quite frankly, outside of the film grain effect (Which I intend to be a toggle option.) I really can't see myself getting rid of the character blinking or the reflections. (The same script will also be used to make mirrors work in the mansion interior.)
On my version of the project I've already tackled some of the issues you've brought up now as well as previously. Particularly, the wall transparency parallel processes have all been merged into one, including the maze's.
The Blocks. Yeah, the eastern servant's house Blocks were pointless... one of those stupid mistakes that slip by when you're tired at the end of the day.

I think I mentioned them in a previous post, and I had them fixed back then. The only Blocks remaining in my current version are used on the northwestern crypt - three of them covering cracks on the wall to prevent the player from moving through them, and twelve total to handle a couple of edges that the player can walk over or below depending on their elevation.
Using a character sheet for the dumpsters is a nice idea. They were in my B tileset for a while, so I ended up using the same method I did for the doors with them. You're absolutely right though, turning them into an actor sprite would be a more elegant approach even if it doesn't impact performance. Likely gonna be low priority for now, but I'll be sure to do it sooner or later... since my accursed perfectionism demands it.
You mentioned the region IDs. I cleaned up all my region IDs when I reworked the Direction Fix event to use terrain tags instead. I did catch the conflict with the bus stop seats too.
As for the maze; it
is available day and night, although at night it turns off your minimap while you're venturing inside it, darkens the area further and reduces the radius of your candle light. I'm not sure what you mean by combining regions for both ends though. Do you mean reusing the region ID for walls outside the current screen position?
I remember ages ago, when the lights started becoming a problem I looked into a proximity based script, but the way it was implemented meant every light had to be a parallel process too. So it ended up breaking even in terms of performance gain. Your solution circumvents that issue nicely, so I'm about to give it a shot!
Once this is over, I'll update the demo link so you can see the improvements you helped me with!