Some thoughts about Long Exposure HDR photography

I have some rather interesting questions... I was researching long exposure HDR photography recently; and that got me thinking; Is it good to take one of the images, the one that's a proper exposure, using an ND filter, then take the others w/out a filter but setting the EV to the desired value? This might not make sense to everyone, since the idea or purpose of HDR and long exposure are different. I thought about it to go for creative effects. Sure, I could just take a single exposure using RAW, however, there's something about HDR software that I really like; I guess it's the way that the tone mapping works. I was thinking also that maybe manually blending exposures would resolve the issues that could arise with such photography. For example, when photographing a waterfall and I want the smooth silky effect of the water, I could take various exposures with an ND filter and then merge them, but the problem that I see is that the underexposed photo might cause the water to be blended in a way as to not render it silky smooth. I think that I might have to use some of my Photoshop skills in this instance! Or, I could just use a very strong ND filter if the sunlight is too strong, so that the short (dark) exposure will have the silky type effect to start off with. I might be in a hurry however. Anyhow, I don't want to get somewhere I want to go and have to experiment there, if someone's already tried this technique; it will save space on my memory card.