A mouse and a keyboard is no substitute for a good HOTAS setup.
HOTAS stands for Hands on Throttle and Stick. A well setup HOTAS means you never have to take your hands off your throttle and joystick. Every single control you'll ever need will be at your fingertips on a trigger or hat switch. My old HOTAS (which needs a serial port... which my current PC doesn't have

) had 6 triggers, 2 4-way hats, and one 8-way hats (useful for looking around the cockpit) on the joystick. That gave me 14 "keys" I could press. My throttle had four triggers and four 4-way hats. That gave me 20 "keys" I could press. If I mapped one pink trigger to shift key, and the other pinky trigger to the control key, the total number of functions I could control, without
ever taking my hands off my controls, was 128 (32 "keys" plus shift+, control+, and shift+control+ combos), plus the joystick and throttle's primary purpose, and the free-look 8-way hat. Use a ring finger trigger for the alt-key, and you expand your total potential functions to a mind blowing 248 (31 "keys" plus shift+, control+, alt+, shift+control+, shift+alt+, control+alt, and shift+control+alt+ combos).
A mouse is meant to be used one handed. A keyboard is meant to be used two handed. You're one hand short to maximize these controls. Chances are your mouse has three buttons plus the scroll wheel. And your keyboard (being one handed), only has access to 27 keys... and I'm being generous here, since some keys are awkward to use without moving your hand too far from "home row". Given that your pinky controls both control and shift, plus another 7 buttons, you can control 76 functions, plus the mouse's primary function and the scroll wheel. And you can't use shift/control/alt combos without either removing your left hand from home row, or your right hand from the mouse... which
could hurt your response time.
There's another advantage to HOTAS beyond the sheer number of potential functions at your fingertips (how many do you need, anyways?) You can map game controls to all control+ or alt+ combinations, and use your keyboard to
chat.
The
only advantage a mouse/keyboard setup has over a HOTAS is the precision of the mouse for aiming while
sniping And in this game, I doubt that'll come up all that often (and if it does, the mouse is still available.)