Hi Kirti --
I second Angie's suggestion to try on as many pants as you can in the silhouette(s) you're thinking about before going custom -- and I'd go a step further and bring a tape measure with you so you can take notes about what's working (or maybe what's not) in terms of measurements.
I'd assess/note:
* waist (also noting where this hits on your body -- X inches below navel etc)
* rise
* leg width (upper/lower)
* lower leg opening
I wear/have worn trousers year-round and really, really prefer wool with 2% stretch. You can definitely seek out a tropical wool for warmer seasons. [My summers aren't too hot in the PNW, but I've also lived in high heat + high humidity climates.]
Reasons:
* wool is super-breathable and has antibacterial properties
* a good wool will resist wrinkling, and the wrinkles will fall out overnight after hanging
As I told Una when she was thinking about a custom trouser suit, I'd look for a 10 ounce worsted/merino wool in the 80s-110s range for "medium warm" through cold temps.
The 120s and up are silky but not as durable and (personal opinion) even lined they feel flimsier to me. I like a nice hefty drape on my backside, ha!
Personally I prefer lined pants for durability and fit reasons but it is very much a personal preference....
OTOH, unless lined in natural fabric (rare in RTW! but maybe you could explore using semi-synthetic-but-breathable rayon or cotton lining with custom) lining does reduce breathability. So I suck it up and will wear unlined tropical wool when it's hot.
Going unlined does up the "lumps and bumps" factor, of course -- something you may or may not want/need to consider.
[Alas, I find even loose trousers can highlight/cup areas when they are blown against one, one bends over, etc. Makes me think a bit harder about what to wear underneath. ;)]
Let us know how your search/experiment goes!