[What I am about to share obviously runs contrary to the OP's intention to go with a 1X setup. But, just in case folks are open to alternatives....]
I offer the following purely as food for thought.
I can't speak to the feasiblity of the following solution in regards to a small wheel bike (for instance, I've never tried it on my 1 X 3X7 Air Glide) but it works exceptionally well on my 26" wheel expedition touring bike (a Fat City Wicked Lite frame w/drop handlebars, Shimano SL-BS77 9-spd bar-end shifters and 175mm crank arms). The result is a silky smooth 790% gear range (877% gear range if I install a 16T cog in place of the existing 17T cog). Curious? Keep reading.
If a 74-110 BCD crank happens to work on a given BF (assuming there's also allowance for a front derailleur) then one could potentially install said crank along with a Mountain Tamer adaptor.
The splined Mountain Tamer Quad Plus:
http://abundantadventures.com/mt_plus.html
...is basically impossible to find but the OEM still sells the splined Triple:
http://abundantadventures.com/mt_triple.html
...along with a selection of splined Suntour "A" cogs.
If the Triple is used with a 26T granny, it can be fitted as a fourth chainring (a "super granny"). Use of a 16T or 17T cog as a super granny allows ridiculous low-end and, along with a 46T big ring and 11-32 cassette, reasonable high-end gearing too (upwards of 108.7 gear inches).
In my case, with a 17T cog installed on the Quad Plus, I achieve a low-end of 13.8 gear inches and a high-end of 108.7 gear inches (w/a 16T cog installed as a super granny the low-end drops to 13.0"). On the one hand, I can practically climb a tree while, on the other, I can pedal at high speeds. I basically never run out of high-end given that I almost exclusively utilize 1.75 Schwalbe Marathon Plus tires. Though I will swap out for wider knobbies if planning long stretches on single track or poor quality dirt roads, I never go with anything narrower. Thus, a 'higher' high-end is pointless to me.
I utilize a Mountain Tamer Quad Plus (which is the splined version of the venerable Mountain Tamer Quad - I scrounged for many years on eBay before I found one) fitted with 17T and 24T Suntour "A" cogs. [Note - I would think that a Triple along with a standard 74 BCD 26T chain ring would accomplish roughly the same result.] That sub-assembly is installed on Shimano FC-M730 cranks which are also fitted with Raceface 34T and 46T rings (resulting in a quad chainring). That assembly is then used in conjunction with a SRAM PG-990 11-32 cassette (11-12-14-16-18-21-24-28-32) and a PG-991 9-speed chain, all of which is shifted by a long cage Shimano RD-M751-SGS rear derailleur and a Shimano FD-M900 front derailleur (via the aforementioned bar-end shifters). Rounding out the drivetrain is an Avid Rollamajig, a Middleburn alloy breakaway rear derailleur bolt and an N-Gear JumpStop (the latter of which did require some minor modification to allow for the super granny).
In my case, the above setup (excepting the N-Gear JumpStop) required zero modification. That said, I did strategically machine away a little bit from the rear SKS P-65 fender (thinking I would need some additional clearance when the chain is on the super granny and on the biggest cog in the rear) but realized after the fact that this was uneccesary as there is plenty of clearance without this modification.
In closing, I have no idea if this setup (or one like it) would work on a given BF (or any other frame for that matter). However, if a huge range is desired - particularly one not reliant on a high-priced and not-widely-available-everywhere-in-the-world wide-range cassette (use of which is accompanied by a frighteningly low-hanging rear derailleur cage), it might be worth a try to see if one could make it work. For the kind of riding I do (everything from open-ended, heavy-loaded, expedition-style touring to fast training rides/day tours/commutes to hauling all manner of loads with a selection of trailers) I get the best of all worlds with this setup. The arrangement is bomb-proof and, once dialed-in (which, for me, was super easy), almost never requires adjustment. It's basically set and forget.
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another great conversation from the Bike Friday Yak!
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