>My assumption is the vast majority of consumer scanners out there will support all 3

Really ?


My scanner is an Epson V100 (and there are lots of epson scanners used under linux, due to it's good support) and the sane epson-backend doesn't support line-art (als I've written sane is inconsistent, binary would be the right parameter with epson-scanners to get black&white)

'Just for fun' my output of scanimage -h

Options specific to device `epkowa:interpreter:002:006':
  Scan Mode:
    --mode Binary|Gray|Color [Color]
        Selects the scan mode (e.g., lineart, monochrome, or color).
    --depth 8|16 [8]
        Number of bits per sample, typical values are 1 for "line-art" and 8
        for multibit scans.
    --halftoning None|Halftone A (Hard Tone)|Halftone B (Soft Tone)|Halftone C (Net Screen) [inactive]
        Selects the halftone.
    --dropout None|Red|Green|Blue [inactive]
        Selects the dropout.
    --brightness 0..0 [inactive]
        Selects the brightness.
    --sharpness -2..2 [inactive]
        
    --gamma-correction User defined (Gamma=1.0)|User defined (Gamma=1.8) [User defined (Gamma=1.8)]
        Selects the gamma correction value from a list of pre-defined devices
        or the user defined table, which can be downloaded to the scanner
    --color-correction User defined [inactive]
        Sets the color correction table for the selected output device.
    --resolution 200|400|600|800|1200|1600|3200dpi [200]
        Sets the resolution of the scanned image.
    --x-resolution 133|200|400|600|800|1200|1600|3200dpi [200]
        Sets the horizontal resolution of the scanned image.
    --y-resolution 133|200|400|600|800|1200|1600|2400|3200|4800|6400|9600dpi [200]
        Sets the vertical resolution of the scanned image.
    --threshold 0..255 [inactive]
        Select minimum-brightness to get a white point
  Advanced:
    --mirror[=(yes|no)] [inactive]
        Mirror the image.
    --speed[=(yes|no)] [no]
        Determines the speed at which the scan proceeds.
    --auto-area-segmentation[=(yes|no)] [inactive]
        
    --short-resolution[=(yes|no)] [no]
        Display short resolution list
    --zoom 50..200 [inactive]
        Defines the zoom factor the scanner will use
    --red-gamma-table 0..255,...
        Gamma-correction table for the red band.
    --green-gamma-table 0..255,...
        Gamma-correction table for the green band.
    --blue-gamma-table 0..255,...
        Gamma-correction table for the blue band.
    --wait-for-button[=(yes|no)] [no]
        After sending the scan command, wait until the button on the scanner
        is pressed to actually start the scan process.
    --monitor-button[=(yes|no)] [no]
        Indicates whether a button on the scanner has been pressed (read-only
        option).
  Color correction coefficients:
    --cct-1 -2..2 [1.0878]
        Controls red level
    --cct-2 -2..2 [-0.0666962]
        Adds to red based on green level
    --cct-3 -2..2 [-0.0210876]
        Adds to red based on blue level
    --cct-4 -2..2 [-0.0891876]
        Adds to green based on red level
    --cct-5 -2..2 [1.15129]
        Controls green level
    --cct-6 -2..2 [-0.0621948]
        Adds to green based on blue level
    --cct-7 -2..2 [-0.0653992]
        Adds to blue based on red level
    --cct-8 -2..2 [-0.517487]
        Adds to blue based on green level
    --cct-9 -2..2 [1.58289]
        Control blue level
  Preview:
    --preview[=(yes|no)] [no]
        Request a preview-quality scan.
    --preview-speed[=(yes|no)] [no]
        
  Geometry:
    -l 0..215.9mm [0]
        Top-left x position of scan area.
    -t 0..297.18mm [0]
        Top-left y position of scan area.
    -x 0..215.9mm [215.9]
        Width of scan-area.
    -y 0..297.18mm [297.18]
        Height of scan-area.
    --quick-format CD|A5 portrait|A5 landscape|Letter|A4|Max [Max]
        
  Optional equipment:
    --source Flatbed|Transparency Unit [Flatbed]
        Selects the scan source (such as a document-feeder).
    --auto-eject[=(yes|no)] [inactive]
        Eject document after scanning
    --film-type Positive Film|Negative Film [inactive]
        
    --focus-position Focus on glass|Focus 2.5mm above glass [inactive]
        Sets the focus position to either the glass or 2.5mm above the glass
    --bay  1 | 2 | 3 | 4 | 5 | 6  [inactive]
        Select bay to scan
    --eject [inactive]
        Eject the sheet in the ADF
    --adf-mode Simplex|Duplex [inactive]
        Selects the ADF mode (simplex/duplex)
    --detect-doc-size[=(yes|no)] [inactive]
        Activates document size auto-detection.  The scan area will be set to
        match the detected document size.
    --scan-area-is-valid[=(yes|no)] [yes] [read-only]
        Indicates whether the current scan area settings are valid.
    --adf-auto-scan[=(yes|no)] [inactive]
        Skips per sheet device setup for faster throughput.
    --double-feed-detection-sensitivity None|Low|High [inactive]
        Sets the sensitivity with which multi-sheet page feeds are detected
        and reported as errors.
    --ext-sane-status 0..3.05176e-05 [] [read-only]
        Ugly kludge to provide additional status message strings to a
        frontend.
    --adf-duplex-direction-matches[=(yes|no)] [inactive]
        Indicates whether the device's ADF duplex mode, if available, scans in
        the same direction for the front and back.

Ah and yes (as you might expect) simple-scan produces colored images if I select text.