Okay, it doesn't look like you're under any illusion here, but I can't resist pointing out that realistically, there's no way an Ultra Tech bow would be a remotely sensible weapon.
That said, onward.
Force blades never care about the ST of the user. Making them into missile weapons wouldn't change that. The Force Blade at half a pound is really rather too heavy for an arrowhead, but you don't need 18" of blade for an arrowhead either, so perhaps you could miniaturize.
The classic way to make a bow do something other than fling pointy sticks is to use gadget arrowheads. UT doesn't directly address this, but...thimble grenades packing 25mm warheads are .06 pounds. That's within the weight range of perfectly reasonable arrowheads. Which means that it's more or less reasonable to have arrows tipped with
any kind of 25mm warhead. (Including the Plasma Lance warheads from the
designer's notes.) Which should really give you all the firepower you need! There are more sensible ways to deliver 25mm warheads than a bow, but there aren't a lot of targets that can stand up to them. If you really feel the need for more, the quarter-pound 40mm warheads
are badly overweight for a normal arrow, but you could still shoot them for a moderate distance.