If you want the magazine safety to remain in the gun, you can polish the end of the safety to a very smooth point and you can polish the magazine where the safety touches it. That will help. Regardless, I removed mine completely.
The trigger can be lightened and smoothed a lot. I know.... my trigger is very nice and easily rivals my 1911 triggers for crispness.
I've found my Hi-Power to be every bit as accurate as it needs to be. It's not a target gun; it's a combat gun that's pretty darned accurate when you make it so.
^^^ Same here. My 1994 model Mk III is a fantastic gun and the trigger is waaay better than what I've read some people experiencing, and waaay better than a friend's pristine T-Series Hi Power (which have the internet reputation of being some of the best-finished HPs).
I'm confident that there is a wide, wide range of trigger quality among the HPs out there. If you get a good one, IME there's nothing to complain about unless you are extremely picking about the trigger on a gun like this.
I don't think my Mk III is quite as accurate as my CZs (75B, 75 PCR, 85 Combat, 97B) but it's pretty close and probably better than 95% of shooters are capable of delivering.
I removed the mag safety but it barely changed the trigger pull because my slider was very slick as was the magazine. The trigger is firm but very crisp, every bit as crisp as my Kimber 1911 but not as light. If I were going to carry it I wouldn't think it needs anything at all, and it's also just fine for general shooting.
I LOVE the Hi Power and keep wanting to pick up another one even though I certainly don't need it. The only rival it has in terms of feel in my hand is the CZ family of 75-based guns, and even then, there's still something special about the size and feel of the Hi Power.