Small terrarium for jewel orchids question

[mrt]

Hi all,
I got a couple of jewel orchids:
* macodes petola
* ludisia discolor var. alba
* anoeoctochilus formosanus
as the days are becoming shorter here, and the days become darker, I was a bit afraid that the orchids may have not enough light (unfortunately, my appartment has only north facing windows, so it is already quite dark).
While I was thinking about making a little growlight (I am an electronics engineer and work with optoelectronics, so I do have loads of different LEDs here, which do have a daylight spectrum which should be fine for the plants) I was searching the net and also came across this board. Some people seem to have their most valuable and sensitive plants in a terrarium.
I do have a 30 x 30 x 30 cm glass containter (was an aquarium before, I guess) and I thought I would make a setup as follows.

I would construct a lid for the glass container which holds the LEDs and also works as heat sink. I could also add a humidity sensor.

Then my idea was to put the orchids, with their pots, into this glass container, close the entire thing with the lid and use the LEDs mounted on the lid as growlights. Add a timer which switches the light on for 12h.

I am unsure about a couple things, though.

a) if this is kept closed, I assume it would grow mold quite quickly, would it? so I would add a little ventilator and humidity sensor and as soon as the humidity is above, say, 80%, the ventilator is switched on. Bad idea?
b) is 30cm maybe too shallow for these little orchids? mine does not flower yet but I saw pictures and I am not sure how tall the flower stalk will be.
c) instead having the container completely closed with the lid, is it maybe better if the lid is partially open and covers maybe only half of the opening?
d) maintenance: I always wonder how people having such a "terrarium" conduct the maintenance. For example watering. I don't want to add a mister, so I guess I would have to remove the pots regularly, water them and put them back into the container. Seems like it is quite a bit of work? however I am unsure how long this thing will stay moist enough for the orchids to be happy. Any experiences? is it perhaps a bad idea to have the orchids within their pots inside this container?