The standard answer is to see your local pro. I am not a pro so I can't offer advice. If, however, you are asking to explore the physics, again I am not a pro but I have given some thought to the problem. Hopefully I can help you gain some insight . First consider what happens when you swing the club. To do this, I suggest you hold the club out in front of you, eye high and horizontal. Look down the shaft and you should see that the club-head sits above the shaft. Consider that if you swing the shaft thru a perfect plane and rotate, the club-head will move down to join the shaft in the plane. If however you swing the club-head thru a perfect plane and rotate, the shaft will rise up slightly to join the club-head in the plane. Try doing these slowly until you can feel how different they are. Manipulating the club thru these two exercises feels very different to me. Swinging the whole club without rotation will feel different again. The following is based on the assumption of trying to swing the shaft on plane. Now if you can imagine swinging the shaft thru a perfect plane, with 90% rotation of the club-head then any momentum built up in the club-head would tend to keep the shaft on plane as you complete the back-swing. If you could manage to swing the shaft on plane without rotation of the club-head then any momentum in the club-head would tend to pull the shaft slightly off the plane. (the bulk of the club-head being outside the intended plane) .It would follow that the effect of an increase in club-head weight would depend on the mechanics of your swing, but it could adversely affect your swing-plane if you do not rotate.
It doesn't immediately occur to me that increasing the weight of the grip might cause some similar problem, but again, I am not a pro so ask your pro. (Unless you are that rare breed that has a perfect swing-plane). Even if you can manage to learn to swing with little rotation, squaring up the club-face will still be required. The more I say the more I realize that I should have quit at 'see your local pro'. Over-analysis does lead to paralysis.