I understand the record company's business angle that it's their job to market your brand of rock n' roll to kids; and it's hard to sell to teens someone who realistically is their parents' age. Remember, to a rebellious teen, their parents are the least cool people on the planet. It's cool that some of us are fortunate enough to still rock out well into our middle age, but rock n' roll will always be a young man's world. Especially the cutting edge of it.
With that all being being said, my personal stance is that I totally agree with the decision you made. I would never make a lineup change just for that reason. Then again, I'm not out there trying to sell records, so maybe that's easy for me to say. I only believe in performance based lineup changes. I especially agree with what you did if the drummer you already had possessed a real good chemistry with you guys. Drummers aren't too hard to find, but good drummers are. I've always felt that one thing every band who "makes it" has in common is a superb rhythm section. There are plenty of bands who made it to radio with average to slightly above average guitar players; but none of them had shitty rhythm sections. That bassist/drummer connection is really under rated, but is really the backbone of any rock band,