I've ordered the mbx6t arms, but they are coming from HK, and have not arrived. I went that way in order to keep my 4WS.
Otherwise the X2 arm conversion looks really good. The other big benefit to using a truggy arm/hub is that you can have a lot of caster which will aid steering.
Personally I have found my HST arms to be much stronger than the my savage's, even tho I've had the truggy longer and have driven it much more recklessly (and Arct1k has seen me drive it at the RCM bashes, so he would agree I did my best to break it lol.)
I've torn out the front part of the Sav arm many times on a front collision. If you see the thin F part of the arm, the front split where the arm brace goes thru, that always gets bend back and tears out. The back part, behind the brace, tears partially but is screwed enough I have to replace the arm.
The truggy et al arms I've seen are thicker and all behind a brace, with the bonus of captured pins.
I don't like the dogbone/cup setup either. My cup is badly worn and sloppy. I'm not so sure that HPI uses thicker parts to make up for weaker materials. Trugs are made to be race tough, altho the newer trugs cut down on "extra" material so much to reduce weight IDK how they will hold up in a bigger truck.
Anyway, I think you are asking alot in one arm to be able to use trug str end, and be able to keep savage axles. I'm pretty sure the Sav knuckle bearings are 16*8*5. Perhaps if you looked at parts diagrams and see which trugs use tho bearings, you could find something close. The X2 does use two sets in ea knuckle, so at the worst you may be able to use XL ext hubs to go all the way thru the knuckle, and shim behind the wheel hex. IDK the width of the chub, but the savage arm end seems large, so I imagine you might be able to fit in there w/ shims.
Those chubs have about 20*+ of caster, so the top arms would have to come back to match up well also. Father forward you can move the chubs, the better as the sav top arm is already in a "rear biased" position in the bulkhead