So,

I have around 100 cacti and succulents. I have grow lights. I have around 13x9ft space. That needs filling.

I'd love to have an indoor desert!

So I was thinking. A two foot deep raised bed lined with a heavy duty pond liner a 6-10inch deep gravel base for drainage, then a mesh to stop soil washing away. Then fill it with loam based soil such as John Innes no2/3 with extra horticultural grit. To fill the rest. And top dress with sharp sand and Decrotive gravel/grit
I am aware I will need to consult a specialist on the weight limit of the floor (in first floor flat)but if it can hold. Grand piano (neighbour had one) it should be okay.
Natural light now the area gets 2-4 hours natural light depends on time of year. Ventilation well I have windows open unless it's frosty!
Heat it's avg.

I hqve desert, and jungle cacti and now a small collection of lithops.

I want your thoughts on it. And any ideas of better suggestions.
I'd prefer not to do a potted one. As the cacti I have can grow fast!!! And slow.
I have a wide array. Including dragon fruit, 14 epiphyllum, a echinocactus grusonii, a Mexican living fence opuntias jade/money tree. Pachypodium, stapelia s, aroids. Aloes maybe I can make it multi layered abd do an alpine part as I have a few others. I may be able to make area bigger but unsure. I have bananas (dwarf Cavendish) jacaranda, columnia, lychee mango, coconut, dumb cane, 5 bromiliad including pineapple (seed and tops) ginger and many more! So I could do a desert, a jungle oh and some orchids! I have around 140 plants indoors abd many more in mum's garden!

So back to original question. What would you do/advise?