That was the best part... and I created lots of modifications to the rules when I was very active in the 1980s... a detailed initiative system, an alternate magic system... etc.
Unfortunately, TSR got into this fascist "if it's not official, it's not allowed" kick for a while, but eventually that nonsense was left behind and WotC has done a fine job with the property (4e notwithstanding).
I hear you, it's always good to stir things up a bit. Personally on my campaigns I like to bring in the Iron Heroes reserve hp system. Basically heroes get a pool of double their max hp as "reserve" when they rest they can transfer hp from this pool to their hp. It eliminates the whole 5 minutes of battle 8 hours of resting problem for adventurers.
As for WOTC I'm really unsure how I feel about what they've done. I read that with 4th edition they also fast forwarded Forgotten Realms 100 years and switched it to the new magic system. I don't really read that much fantasy anymore but it still bothers me a little that the Realms I knew and loved are now gone. Kind of reminds me of that old Dragonlance 5th age thing. Oh well I guess I'm just getting old, I'm sure there's lots of people who enjoy having a fresh start. In other news I'm really excited that Shadowrun seems to be making a huge comeback! There's also seems to be some action on the Darksun front, it's really nice to see some of those old favorites that I felt never got a fair shake rise from the dead.
Unfortunately, TSR got into this fascist "if it's not official, it's not allowed" kick for a while, but eventually that nonsense was left behind and WotC has done a fine job with the property (4e notwithstanding).