The thing about MM, is that Rolling the ball is Physical. It took a lot of work to get it moving fast, and you could accidentally overshoot once you got it moving good. It was part of the challenge and fun of the game. The game itself is short and almost no gameplay at all. It was all atmosphere and controller oriented.
If you use it in mame with a digital control, you would have to set the digital acceleration very high. Which is basically cheating... because you are getting acceleration and speed that would normally be either impossible, & or take a Ton of physical work and "time" to achieve. Thus the game will be too easy (without considering the precise steering)
With a real trackball, on a real machine, on the stock settings, its Really difficult to get through all the stages without running out of time. Every moment is Crucial. You dont get that sense of urgency or difficulty with digital control.
Now, I know what you mean about the digital control however. I do like controlling a games like the PS1 version of Ridgeracer with the digital controller better than a mini analog controller, but the main reason is because mini analogs are poor as far as controllable leverages goes. A real wheel would be better, but you dont always have one laying around, and the code is adjusted to handle digital control fairly well. The difficulty of the game has little to do with acceleration, so digital accel is fine and wont effect timed challenges. Anyway, as said, the game is designed to control with digial - and thats fine. But MM, its just not right to control is with anything other than a real trackball.
A better example would be Missile Command. Id love to see you score well on MC with a digital input. You wont last more than 5 rounds if that. You have to use a mouse at Least, and even with a mouse, its not as fun as with a true trackball.
Atari XO football is another example... where its more fun and challenging to use trackballs. The faster you roll, the faster the men run. You get a real workout on that game, as its trackballs are a heavy 4" diameter, and you have to roll really fast to move fast. Controlling a game like that with a digital control will work.. but its not as fun or challenging.
What about SuperSrint? Id love to see you play even 3 levels well with a digital stick. Even a mouse wont be much good there. You need a real spinner to do well in that game.
And Spy Hunter? This game is Brutal Period. There is almost no way you can last for long after your 'grace' time is up, if you are using some digital control scheme. The game relies heavily on precise acceleration control, as well as aggressive steering, gear shifting (mamed Button toggle shifter RUINS this game), and weapon use. You could get away with it on a Nintendo programmed version, but not the real deal. And even if you could do OK, you would do 1000x better with the true controls.
And then we have a game like Hard Drivin. This game is not graphically that impressive at all. But it was hella fun to play. The controls on the sit-down were the very reason this game was so popular. The wheel has a motor strong enough to turn a dryer full of rocks, and its force feedback is so good that it rivals most modern FFB games. You felt everything that was happening with the car, from loss of traction, to effects from the cars mass shifting. The Gear shifter was also a huge feature. It was built like a tank, and yet felt so perfect as it sprung-clicked into place. Even the brakes were revolutionary on this game. They used a progressive pressure assembly, so that the further the brake was pressed in... the harder it was to press them. It was extremely realistic, and gave really excellent & super precise control. Far exceeding any other racers brake pedal system. All of this adding up to make one of the more popular racing titles in gaming history.
Playing RD in mame, with no force feedback, and without the 10 turn dryer-motor wheel... no super-shifter, and generic pedals is bad enough. But playing it digitally, is 1000x worse than if you actually hooked up at least a standard Steering wheel & Pedal set. Basically, the game is all about the feedback and specialized controls. Nobody who has ever played the original sitdown can ever deny that.
Mame has come a long way as far as arcade input possibility is concerned. However, a simple thing like Shifters is completely ignored.. which is mindblowing... and really ruins a ton of great race games for people who Really have great passion for them, and want to play them with real controls.
Anyways, thanks for your verbal agreement about the 720 issue. More people really should speak up.. but most are fearful that a dev will cry and quit all the sudden. Or that they are made to feel as Ingrates for even asking or suggesting something.