You can definetly parse the output of the --help for this.
Actually, I wrote a little script to help me, but its in Lua. (I was lazy and did it in like 10 minutes flat with CTRL+C).

Also: I want to expand the OptionParser parser("wabt-tool", s_description); stuff, to include proper description so it is distinguished from the short description. Would that be ok?

Format:

usage: <usage>
<short-description> one liner; no indentation
\n
  full description
  indented by 2 spaces!
\n
examples:
  # sample-description
  # may span multiple lines
  $ sample input
\n
options:
  -x, --xyz     two (2) spaces indention for "multi-option"
      --abx     six (6) spaces indention for "single-option"

The Lua-script:

local line = ""
repeat
	line = io.read('*line');
until line == "options:"

local FULL = "^      %-%-"
local SHORT = "^  %-(.), %-%-"
local R_FULL = ".It Fl Fl "
local R_SHORT = ".It Fl %1 , Fl Fl "

for line in io.stdin:lines() do
	if line:match("^ +%-") then
		local parsed = line:match(FULL) and
			line:gsub(FULL, R_FULL) or
			line:gsub(SHORT, R_SHORT)
		print((parsed:gsub("   +", '\n')))
	else
		print(line)
	end
end

P.S.: I would like to add the option -m, --module=[NAME:]PATH use PATH as a wasm module and provide all exports under the name NAME (filename if not present) for imports
Later maybe dlopen/GetModuleHandle could be supported? you could simply write your own wasi and wasi will just export wasi.[dll|so] and start the function, done. easily replacable wasi runtime. good for experimentation.