Which Shimano crankset? there have been many sorts..
if you can get a TA Cyclotourist Crankset, they allow 2 chainrings of wide difference
to be paired together.
On a bike tour down the Cal coast my companion from Britain had a 50tooth ring and a 28 tooth ring.
A hybrid drive train using schlumpf planetatry 2 speed crank is another approach
his 2 overdrive cranks are 1.6X and 2.5X the size of the small chainring
He also manufactures, in Switzerland, a reduction geared crank, I have one of those
That I fitted on my Brompton Folding bike, to accompany its 3 speed hub..
In my case the chain never leaves the chainrings on either end, as both ratio changes are internal..
My 54 t ring is in effect a 21.6t granny .. the 50t ring size divided by 2.5 comes out an even 20t.
on my 16" wheel bike.. low is 17" high is 77 " which is excellent for my purposes.
In derailleur bikes triples with a 58 94 pairing , or a 74 110 bolt circle pairing will work too .
in the 80's, attracted by shiny objects, i used a Campag triple as a double..
Middle 52, inner 36, outer a cyclocross chainguard.
it is 144, the inner an 86 mm , machined into the crank arms
Gipiemme triple arms were thickened to suit.
back then 13 t was as small as cogs on derailleur bikes were.