Tl; dr
Black Mesa should play and feel like Half-Life 2 as much as possible, those who have played the sequel but not the original will find it easier to adapt to its familiar play style.
Jumping
[COLOR=‘Red’]-Make it easier to jump up onto ledges the same height or lower than the player, as in HL2
-auto boost when jumping out of water onto ledges in Quake and HL1 needs to return
-height and speed should be the same as HL2
Ladders
[COLOR=‘Red’]-all mechanics should work the same as HL1 and HL: S, free movement, auto mount, etc.
Grenade
[COLOR=‘Red’]-needs to be thrown more centred to the screen like HL2, currently it is thrown too far right and is easily obstructed by walls
Houndeye
[COLOR=‘Red’]-sonic effect intensity (optional)
Crossbow
-BM and HL2 style zoom (optional)
Soldiers
-reaction time is fine, but their accuracy should be lower on easier difficulties
MP5
-burst and auto firing rates (optional)
Crowbar
-view bob when swinging (optional)
-swing speed should be the same as in HL2
Player
-strength for throwing objects should be lower
-BM and HL2 style death animations (optional)
-BM and HL2 weapon sprint animation styles (optional)
-BM and HL2 style weapon sway (optional)
-HL1 style screen glitch indicating crouch jump has been activated (optional)
HUD
-remember last weapon used in sub-category (optional)
-on-screen display for using trams, currently it is difficult to tell if tram has been engaged or not
-counters turn red when supply is low (optional)
-damage indicators show when taking fall damage (optional)
-HL2 style crosshair for HUD zoom
-fire immediately after using HUD zoom as in HL2
Bugs
[COLOR=‘Red’]-View roll selection does not save after quitting
-Cannot turn off radioactive screen noise
-Auto aim always appears enabled
-c2a2c, door near the rocket control room leads outside the map, glass shouldn’t be breakable
-Strange line appears on the shotgun when using flashlight