i think removing the quicksave would work fine. it could still autosave checkpoints and you wouldn't have to start all the way over if you died. but you wouldn't have the luxury of saving whenever you full health and armor.
Behold! Combine Piñatas!
http://www.mustangmods.com/data/11972/d3_c17_050000.jpg
http://www.mustangmods.com/data/11972/d3_c17_050001.jpg
http://www.mustangmods.com/data/11972/d3_c17_050002.jpg
A Combine Holiday Wreath!!
http://www.mustangmods.com/data/11972/d3_c17_050003.jpg
And some more...
here's how i did it:
1) play up to the part where you actually get the gun.
2) changelevel to a map before that (ex. d1_trainstation_05)
3) sv_cheats 1
4) impulse 101