It is possible. Anything is possible.
Without screw holes, it is a LOT harder. I don't personally feel it is worth the effort as I would want to do it as structurally and aesthetically sound as possible. But, it could be done.
Ideally, the tang would have included two good screw hole locations..... But..... it doesn't.
As Leatherman said: It would probably require an epoxy insert or some comparable very well custom fitted insert of suitably strong material that would need a lot of hand tuning.
Without an insert and proper screw holes, you risk having your scales shift. The shifting could be minimized and possibly eliminated by using some epoxy just on the minimal perimeter of the tang. But, you also need something to serve as a spacer at the area were the screws go through or you will bow, bend or crack your scales. So, you really need an insert to fill the hollow tang.
The epoxy method (with the right epoxy) would be the easiest. Otherwise, you would need to shape a piece of semi-hard material to make a spacer. It would ideally need to be pretty tight and probably need to be epoxied into the center and then sanded flush.
Personally, I would probably shape an insert out of aluminum, brass or micarta or similar and epoxy it into the center and sand flush. These materials would be suitably hard and dense enough, but are much softer and easier to work with than metal. Just a matter of finding a piece of stock material in the right thickness. I wouldn't want to spend to much time thinning/planning stock to fit in thickness!
If you have the proper tools, you can even make a skeleton insert to keep the weight down, but a lot of work unless you have the right tools and know how.
Another option would be to design your scales to go pretty high into the ricasso and all the way into the guard and add 4 small pins - 1 at the top of the ricasso, 1 in the middle of the guard and two at either side of the lanyard hole - or just use the lanyard hole as a pin hole at the rear and drop the lanyard option (???) This pin arrangement should save you from having to make any type of insert and would keep the handle skeletonized (= light-weight). I don't think you could likely use screws for this. Knife handle screws are generally larger and would require holes to be too large for the small areas at the front. If you use the lanyard hole, you might be able to find a screw to fit that hole.
Process for drilling holes and setting pins:
*** Probably strip coating and sand tang flat 1st! *** See below!
Drill holes in tang
Clamp one side of scale to tang and drill through tang into scale on back side
Duplicate for second scale on other side
I would personally epoxy the perimeter of the tang
Set scales and pins
Clamp
Let dry
Grind off excess pins
Then you need to shape and fit the scales, etc.
*** To shape and fit scales on a coated tang, it is tough (near impossible) to not sand "on" the tang and mess up the coating. It is easiest to set the scales and sand to fit, but you would sand off the coating on the tang. If you intend to completely strip the blade (- which also requires sanding and polishing a lot to make the knife look decent), then this is an option. Otherwise, you have to hand tune each scale un-attached to the tang. This would be a LOT of back and forth on shaping and polishing = PITA! I don't think you want to do this. This would create MAJOR frustration!
I am about 99.99% sure Busse uses CNC for precision cutting of tangs and scales for fit match. And I feel pretty confident, they match each tang and pre-fit scales prior to coating blades. - Then assemble after coating. I have not personally removed any scales, but I have seen pics of marked tangs. I assume this is to match up scales to matched tangs.
If I were going to do this project, I would go ahead and strip the Swamp Warden, satin finish the blade and ricasso (making sure to keep the tang flat with no "rounded over corners", make the spacer if using a spacer, drill the holes, (I would use epoxy - some don't), set pins or screws, clamp scales to let epoxy set, sand the scales to fit, buff, finish, etc.
Considering the work needed to do it right, you might just consider buying a Game Warden with attached scales and with INFI instead - and call it a day.
These things are much easier in production and if designed to accomodate screws vs. per piece after coated and without screw holes. You are having to go backward the HARD way before you can go forward on this project. But, for somebody who loves the Swamp Warden that much, just has to have scales and wants a somewhat tedious project - there you go.
Here are some links to a couple of Randucci modifications with scales added to a skeleton Game Wardens:
http://www.bladeforums.com/forums/showthread.php?t=459989&highlight=randucci
http://www.bladeforums.com/forums/showthread.php?t=451831&highlight=epoxy
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