HoTT can work well for sci-fi, but - oddly - you might get more out of D3H2, the unofficial combined DBA 3.0/HotT 2.0 rules. You can get them from Tom Thomas on the Fanaticus forums (and here too, sometimes), although you need to have both rulebooks to use them.
One reason that they might work well for sci-fi is that shooting ranges are longer and there are more varied missile-using troops (Bows and Crossbows as well as Shooters, plus Psiloi, who would work well as scouts, etc.). And there are Fast and Solid versions of all troop types, which gives you more variety yet.
Also, it's probably worth looking at
this thread if you haven't already.