Free translation / making it succinct :
Despite being specifically asked about SF and MK, I'm going to talk about Killer Instinct. 4 buttons wouldn't work for this game. LC, you are not allowed to have this opinion about there being too many buttons because I dictate that if you play fighting games you must like at least 6 buttons. Sorry, not sorry. In an attempt to be funny, I will suggest you put buttons near your feet and use those instead of having them on your actual control panel. In an effort to make my post more verbose I will also suggest the SF kick buttons near your feet could be used for running and blocking for Mortal Kombat, see its funny cause you kick and run with your feet. Joke doesnt really work for block but hey, lets be honest it wasnt funny in the first place.
I give it a 7 on the Drama Scale. Good work.
I wasnt joking about foot controls. If someone doesnt like clutter on the CP, one can put pedals on the floor.. which can also double as gas/brake for racing games. As well as for possible alternative controls for rare / expensive / unique controllers. Such as using it as a replacement for up/down in the aiming of Discs of Tron. Its never going to be great... but playing a game without the intended buttons isnt going to be great either.
The idea of shoulder buttons on an arcade makes Zero sense. If you feel you can play with a Snes controller... then why not put a Snes jack on the cab? Personally, the shoulder buttons were far too slow and awkward for me to utilize in KI, or SFII.
If you put smaller buttons in on only the two.. it will look odd, and may feel odd as well.
If space is a concern.. Nake the button spacing tight. Just barely enough so that you can still turn the button nuts without getting stuck. You can even place the buttons closer in proximity to the stick.
Or.. make or buy smaller buttons for All of the buttons. In this way, you will have reduced space, same feel across the board, same finger positions for precise no-look activation, and a uniform look... as well as retained functionality.
Ive always thought the standard arcade buttons were a little on the large size personally.
As for SFII, Its been a long time since Ive played.. but I believe there were instances in combinations.. where you could use the quicks to good advantage. However, its far more needed in other fighters.. such as KI. Which, once you get used to its system of combos, is well worth the efforts and extra button space.
As for MKIII.. I cant imagine trying to play it without the run and block being easily and quickly accessible. That game is lightning fast.. far faster than any SF game.. requiring very quick reflexes at times.
And finally, when many people play games from their past.. they want to play correctly.. and not with some hack. For example.. Playing Defender with an 8 way joystick without a reverse button... doesnt feel right. Playing Asteroids Deluxe with a joystick, without the full leaf button setup... also feels wrong. Sometimes these hacks can give you an edge... and to a fan of these games.. they dont want that 'cheat' methodology. Other times, hacks can be far more cumbersome, making it harder to play accurately.. and ticking off a good player, due to their inability to get the game to do what they can easily do on the real controls.
There is also the level of comfort involved.. as well as the look and feel. Which is why many will have at least one real Leaf button on their CP... for far faster fire rates on classic games. Theres also far less fatigue when using them in rapidfire games.. compared to microswitches.
Im being genuine with my advice and ideas. But do as you please. Its your hardware, and your decision to cripple your experience.. rather than rise to the challenges, with time and efforts.
If its mere construction time on sellable builds.. then simply charge more, for your additional time and efforts.
You cant force people to cripple their game experience.. and expect them to be happy about it. But, you always have the option of not accepting their orders too.
Furthermore, as much as Malenko may find foot controls laughable.. they are used regularly in various fields and games. Everything from Driving vechicles, to running mechanical presses / machines, sewing machines, organs, guitar pedals, flight controls, and far more.
And yes.. it would be interesting (I have thought about it), to make a kick/punch system for game input. It would give quite the workout. heh I believe its been done.. by a few different companies in different methodologies.
(Plus.. physical contact is far more fun than swinging a controller through the air in empty space.. and never registering any actual feedback + poor control to boot)
+11 for the Gymkata clip

I remember seeing that Ages ago as a kid.
Cheesy and unrealistic,but it was fun back then. Not sure I could say the same now. Experience in combat really changes your perspective and enjoyment levels of things like this.