Hmmm, not sure if there's an easier way to do it... I do know that there is an "animated" type of HUD, though haven't used it before.
If you do want to use the method you depicted, then here's a starter:
:state=0:<load all of your HUDs>,timerstart,hudshow=frame1,incstate
:state=1,timergreater=500:hudunshow=frame1,hudshow=frame2,timerstart,incstate
:state=2,timergreater=500:hudunshow=frame2,hudshow=frame3,timerstart,incstate
Then just keep going for however many frames you need... in this example I'm assuming you've named your HUDs "frame1", "frame2", etc. for simplicity.
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