paramount3

I've done a fair bit of forum searching and have found some options to try, but I don't have high confidence in any of them. Hoping for some help. My situation:

I'm building up a road-biased gravel bike based on a steel Kona Rove ST frameset, 31.8 mm diameter seat tube, will run with 32-37mm tires. Kona sells the complete bike with a 1x11 drivetrain, chainline 45.5 mm. I want a wider gear range than the stock 11-42 range, and especially I want easier low gears. I have the first-generation Tiagra 2x2 hydraulic shift/brake levers ST-RS405 (which are functionally equivalent to the current ST-4720 levers). These levers are 10 speed, but with the same cable pull as current Shimano road 11 speed systems, which means that they can be used with current 11 speed front and rear derailleurs (eg the GRX RX810 and RX812), or with the few 10 speed derailleurs that use this pull, which as far as I know is restricted to the Tiagra 4700 series and the GRX 10 speed series (RX400 I think). Anecdotally, these levers don't work with Shimano MTB derailleurs due to differences in cable pull.

My question: What is my best option for a 2x10 setup to get my desired gearing? Specifically, which crankset and front derailleur should I use?

Ideally I'd have something like 26/36 low gear, and 44/11 top gear, but I'm willing to give more off the top if pressed. After trying a 1x10 setup, I have decided that a good compromise would be 2x10 with an 11-36 cassette with 42/28 or 40/26 double crankset. Maybe even 40/24 if I could get that to work.

I have a Shimano GRX RX812 rear derailleur that I will probably have to trade for an RX810, and I'd like to stick with one of these clutch rear derailleurs if possible.

Note: the two front derailleurs that should work with the shifters have chainline of 43.5 mm (FD-4700b) and 46 mm (FD-RX400). Note also that an FD-4700b is on its way to my mailbox now, while it seems impossible to get an RX400 front derailleur at the moment. FD-4700-b specifies a large chainring of 46-52t and a max capacity of 16t

Here's what I can try using (mostly) parts that I will have on hand:
1. Existing old square taper FC-M900 XTR triple crankset (47.5 mm chainline with 107mm bb spindle), running 42/28 on the middle/inner positions, which should give an effective chainline of about 44mm. Paired with FD-4700-b front derailleur. Possible issues: front derailleur might not work with the smaller-than-specified chainrings (42 vs 46t large, 28 vs 30t small). Possible chainline issues. Possible chainring spacing issues (or at least will be hard to choose the correct chainrings). Could I try chainring spacers?
2. Existing Shimano Deore FC-M615, 170 mm, 40/28, chainline 48.8 mm. Will try with the FD-4700-b even with the chainline mismatch. Might try one of various MTB FDs that I have. Possible issues: Same as option 1, but maybe more chainline issues. Could I try chainring spacers?
3. Sram (or RaceFace, etc) direct mount crankset with a 2x spider. I happen to have a brand new X0 (I think) set of 42/28 rings mounted on a spider, 120/80 BCD. I don't have a Sram direct mount crankset, however. Which crankset would I have to buy to use this ring/spider set to get the desired chainline?
4. I do have a SRAM X7 crankset that is not direct-mount, but I could mount the 42/28 chainrings on this to try. However, this crankset has a chainline of 48.5 or 49.5 mm.

Long post, lots of details, but I know others have faced this situation, and I'm hoping there's an optimal solution out there. Thanks.