Batch fade between frames on gif animation?

Since you state about 16 Frames that is not many frames for a fade out fade in Tween does support layer opacity and layer positioning animation I feel an animation should have a frame rate if at least 10 fps rate video is normally 30 FPS.  Here is a 16 Frame Frame animation. Red fade out, Green fade in, Text moving. No frame delay.  Loop forever.

100 Frames

Try this script. It sets the transition between all layers of the current video group. The duration and type of transition can be specified when calling the function. Color transition is not used in the code, but it is possible.

#target photoshop

var s2t = stringIDToTypeID,
    transition = {
        fade: 'opacityDissolveTransition',
        crossFade: 'crossDissolveTransition',
        fadeBlack: 'blackDissolveTransition',
        fadeWhite: 'whiteDissolveTransition'
    },
    p = app.activeDocument.activeLayer.parent,
    len = p.layers.length - 1;

for (var i = len; i > 0; i--) {
    selectLayers([p.layers[i].id, p.layers[i - 1].id])
     addTimelineTransition(2, transition.fade)    // < set duration and type of transition
}

function selectLayers(IDList) {
    var r = new ActionReference();
    for (var i = 0; i < IDList.length; i++) { r.putIdentifier(s2t('layer'), IDList[i]) }
    (d = new ActionDescriptor()).putReference(s2t('null'), r);
    executeAction(s2t('select'), d, DialogModes.NO)
}

function addTimelineTransition(seconds, typeOfTransition) {
    (d = new ActionDescriptor()).putObject(s2t('using'), s2t(typeOfTransition), new ActionDescriptor());
    (d1 = new ActionDescriptor()).putInteger(s2t('seconds'), seconds);
    d.putObject(s2t('duration'), s2t('timecode'), d1);
    d.putEnumerated(s2t('placement'), s2t('transitionPlacement'), s2t('join'));
    executeAction(s2t('addTimelineTransition'), d, DialogModes.NO);
}

Very little stuff of the animations features can be automated since it's kind of thrown on as an afterthought, so I don't think you could create an action or script. If you do this a lot it may be worth learning After Effects to at least generate image sequences that can then more easily be converted in PS. AE would at least allow you to tweak multipole settings at once and re-use animations by ways of animation presets.

Mylenium