Changing to any new (different) racquet can be a little rough on the arm, just because it will handle a little differently than your familiar player and you'll likely rack up a few extra mis-hits as you adjust to it. Making a switch can be terrific if we get lucky and land on the right racquet right away, but you won't know whether you'll have a decent fit with a different frame until you jump in a play with it for a bit. The upside of demos...
Switching to a two-handed backhand comes with no guarantees. I honestly know a decent local club player (not one of my students) who got serious tennis elbow a few years ago after switching to a two-hander. If your aptitude is stronger with using the one-hander, it can likely work fine for you with a combo of improving any possible troubles with technique along with getting away from any poly string for at least the short term. You might even need to protect your elbow by learning/employing a slice backhand a little more often.
Step #1: Dump the poly!! Poly strings will make any racquet play rougher on the arm than softer strings; syn. gut, multifiber, or natural gut. Natural gut is the undisputed champ in terms of promoting a more happy arm/elbow, but you might get all the comfort you need with less expensive multifiber or moderately (and affordable) soft syn. gut.
Lots of "racquet technology" innovations are just gimmicks, but the Kinetic design features that ProKennex have come up with are the real deal in terms of promoting arm comfort.
There could easily be more than just one right answer if you go for a different racquet. Hopefully you've already landed on a good fit for you with the VCore 98. Yonex quality control seems to be tough to beat.
I've used a pair of the Dunlop CX-200 Tour (18x20) since the early spring of this year and it was quite comfortable for my 57-year-old arm strung with a bed of 17 ga. syn. gut at around 55 lbs. I added lead tape to their handles to get a more familiar balance and I can say that these frames have exceeded my expectations (I was worried that they would be too light and unstable for me).
I'm in the middle of transitioning into mildly lighter frames than my older 12.5-12.7 oz. arm-friendly Volkls (C10's and O10's). The Dunlop 200 T's have been fun, but I also just pulled out a Prince Phantom 97 (strung with 16 ga. syn. gut) that I picked up on sale perhaps a year ago. Because this racquet was different from my regular players when I first bought it, there wasn't much of a love connection through early trials. The Dunlops were my next sampling and although they've been fun, I haven't found that home-sweet-home confidence with them like I want with my go-to players.
Now that I've had the Phantom 97 back in action for maybe two weeks, I can say that whatever I was missing with the Dunlops is absolutely there for me with the Phantom and I'm getting at least one more Prince for myself this week. At least for me, the comfort and performance I get with this frame are superlative. If you need options to think over going forward, I think that both of these racquets are quite good.
Also remember than any racquet that's a little heavier than your personal normal might turn out to be fine for you with enough head-light balance to give it a comfortable degree of maneuverability. If your Blade is a little sluggish for you, maybe try adding some weight to your handle (I like to put 1/2" lead tape under my overgrip) to get a couple extra points of HL balance. With softer string and different balance tuned in, you might save yourself from the process of shopping out a new racquet.
Good luck with your quest
