When I shoot in an overcast day or shoot a long-term sequence (over 2-3 hours), I get a JPG sequence with exposure adjustments.

I can HG it in Visual Workflow (w/o Visual Preview), or deflicker it in Basic Workflow, but I can't do them both in one workflow.
Multiple exports reduce quality.

I know it's Adobe DNG's problem that JPGs can't go Visual Preview,
but all I need is a HG process with Basic Deflicker together as a workflow for single export purpose.
Can you please add it? Thanks.

ps. I can't always shoot in RAWs. Too much costs for a non-pro TL player.

The easiest way for you would be to convert your JPG sequences to DNG in Lightroom (!) - then just use the visual workflow, as if they were RAW files.

If you don't want to do that: consider that the workflows in LRT are just a bunch of ordered buttons.
You can anytime switch between the workflow tabs, if you know, what you do.
So - with jpgs - just do the visual workflow until you get to the end of the second row, then switch to the basic workflow, apply deflicker, save and go to Lightroom to export and render.

BTW: RAW shooting has nothing to do with costs or "pro" timelapse shooting. It's just the best, easiest and fastest way to get nearly any timelapse done. JPG sequences have inferior dynamic range (especially when shooting the holy grail this is more then noticeable) and take much longer to process due to different reasons.

Thanks! That's very helpful!

ps. I meant the costs of SD/CF cards and HDDs...

The cost of SD/CF cards are negligible today. A 128GB card is under 40US$ - http://amzn.to/1lwDE8O