Rotor makes a 11-46 12-speed cassette. Coupled to a 50-tooth chain ring, I’d give you very similar range than your current setup. You can adjust the chain ring size to either get a slightly easier climbing gear (48 teeth) or the same top end gear (52 teeth).
In my experience, it is almost always better to prioritize climbing gears.
What’s the 48/35 with the 10-36 look like in terms of equivalents? There are several SRAM options for front chainrings that adjust the range. Or you could go 10-33 with one of the smaller chainring sets and get closer spacing, too.
How could a 12 speed cassette have a similar range and spacing to a 13 speed cassette?
What’s the 48/35 with the 10-36 look like in terms of equivalents?
Almost identical to 52-36 with 11-34 cassette.
Or you could go 10-33 with one of the smaller chainring sets and get closer spacing, too.
In my opinion 10-33 doesn’t have enough range for 1x setup.
Similar ≠ identical. In case 12-13 speed, it is possible to make bigger jumps at the higher part of the cassette. For example: 10-44 XPLR cassette has 10-11-13-15-17-19-21-24-28-32-38-44 teeth, I don’t like 2 tooth jumps at the 11-13-15 part, and I would prefer something like 10-11-12-13-14-15-17-29-24-29-35-42.
Remember that 12 spd SRAM road systems require a flattop chain, which also has different specs for the cassettes. There are varying reports re: using a non-SRAM / flattop cassette with a flattop chain. Conversely, you can use a regular chain / cassette, but then you may have interface issues with the crank.
The 1x SRAM chainrings are actually approved for both flattop and older Eagle chains. But, either way, the aftermarket cassette options for SRAM are not widely used for a reason. They’re just not that good.
I’m with you on the gear jumps low on the cassette. 
Shimano has changed this with the 12-speed groups. The old 11-34 was really jumpy at the bottom of the cassette…
Here is the 12-speed 11-36: 11-12-13-14-15-17-19-21-24-28-32-36T
Unfortunately, there isn’t anything with this type of progression with lower gears, but hopefully someday!
Garbaruk has 12 speed 10-44 with 10,11,12,14 and 10-48,50,52 cassettes. Or you can wait for 13spd XPLR and hope for better spacing at the bottom
Yeah that 13th gear really helps with the two tooth jumps. I don’t know of any 12 speed cassettes for 1x systems with the range you are looking for that don’t have that compromise. A 6+ tooth jump at the upper part of the cassette is still significant. Big cadence adjustments when climbing are necessary when I ride them. When you go 1x, you have to learn to adjust your cadence to your effort. No amount of tweaking the cogs by a tooth here and there changes that. Only an extra gear or two can fix it.
Depends on the terrain. I used to have a 10–36 cassette and was able to climb the mountains of Japan no problem. I live in the German flatlands now and I don’t need the range afforded by 10-33.
If I could make a wish, I’d want a 10–39 or 10–40 cassette by SRAM.
it’s 11spd but there is the XG1199 11-42 by SRAM. weighs in at about 200g as well. If you live in the flatlands this should be more than enough.
What I was going to say. But learning to use the different system could prove both comical and useful. They say if you mix things up, you can stave off the issues old age often brings. 
Is it still true that SRAM cassettes are a small fortune compared to Shimano?
Yes, you are right. I should correct my words, not “doesn’t have enough range” but “doesn’t have enough range for me”.
10-36 with a 48t chainring is almost the same as 52-36 with 11-28 (my current 11 speed setup).
I live in hilly area and 36-28 is not enough to stay in my zone 2 at incline over 7% with comfortable cadence. But I can’t say, that 36-28 is as bad, after all I use this setup for two years, and I used 53-39 with 11-28 for 5 years.
Just if I spend money for upgrade, i want all in one, wide range, 1x, 1 tooth gaps in the lower part of the cassette, electronic shifting.
If Sram deigns to make 13 speed for all AXS derailleurs with software update, it will be amazing and I will buy Rival AXS without hesitations.
need to get the UDH hardware update first though…
If you dropped to a 46-tooth chain ring, you’d get essentially the same lowest gear as with your current setup (1.28 vs. 1.29). You’d sacrifice only a tad at the top end, 46:10 = 4.60 is a bit harder than 50:11 = 4.55 and a bit easier than 52:11 = 4.73.
Having lived with that setup in the mountains (with a smaller 42-tooth chain ring), it worked very well for me and it might work very well for you.
Could you share why you want to go 1x?
I haven’t noticed any significant weight or simplicity savings when looking at electronic 1x vs 2x, so I’d love to know what I’m not considering…
Mostly, I wanted to try something new. I like how a single chainring looks. Among other cyclists 1x setup look unusual and interesting.
From a practical perspective, I realized that I primarily use the big chainring, I can ride at 52-23 or 52-25, and shift to the small chainring only when my speed drops below 25 km/h, so I use only 4 last cog with small chainring at the front. Effectively 2x11 turn to 14-15 gears that I use, so I can switch to 12 speed 10-36 with 48t chainring and get almost the same gearing that i have now. And with 13 speed 10-44 ekar cassette I can get wider gear range with acceptable gaps.
As for electronic - I have frame with full internal routing, and 4 houses are just pain to route.
Ultimately, I believe this is driven by consumerism. My mechanical Ultegra groupset works flawlessly, but the allure of new technology is tempting, but why not try a new technology?