I love the stacking in the game. It allows for great points, and to rush you through a bit. It all fairness, the modes in TSPP don't have all shots lit, only monorail, but you have to return to the couch to reset. In fact, in trying to think about this, each mode other than mono has only one shot lit at any one time... Wiggum starts with three, and goes to one, but really, you're going to the otto first, but that means for the most part even if you stacked three modes, only three shots for the most part at any given time are lit.
Not to mention that TSPP is also one of the most difficult machines to restart a mode on: right orbit, hit garage, enter garage or treehouse, upper left to behind TV, but you usually want to bat around the unlock a lock first before starting. Although I have started I believe three to four modes at once before, it's not easy, and all the stuff to even get there usually times out the first, and I can't imagine you doing to well on the second with the time left. When I do stack modes, it usually happens with homer's mode, as it's a natural transition back to starting another one, provided you work in the right orbit at some point.
I like stacking for any machines, and maybe that's just a personal preference, but in games where it isn't, I usually feel it should be there. But I take each game as they are presented for the most part. TOM is a "you are doing this now" with no stacking whatsoever, LOTR allows stacking with MB's for modes, but modes can't be stacked. TZ and TAF allow everything to be stacked. I enjoy what is presented.
In all fairness, you never really do as well at each mode if you have too many stacked anyway, it's more for getting through the modes, rather than giving you a better opportunity to do well at each. In TAF, I try to avoid, and don't like when I stack tunnel hunt with séance, as if you light the mode start again by hitting the ramp while doing the tunnel hunt, then you are going to start séance when hitting the chair, and then you are racing to get the last 15m shot of each mode, which are big important point shots for this machine, and the time for each allows for only a small amount of error. Nice touch mind you, as you have to really consider your shots.
As for the female voices, meh. I guess it would be nice, but all of the call outs now are so well done, I wouldn't want to lose any of them. I think this is so small of an issue as well, not under minding your issue of though, because most people that haven't been actually *told* about this, don't even realize that a female voice is not in the game - I didn't. You're like, "oh yeah...." when you first read about this, which means it's not really all that missed.
If I had my say for what changes I would like for TSPP, I really can't think of anything other than speeding up the return of the otto shot, or just making that loop instead of stop. I really think the game is near perfect. The height of Stern was seen when TSPP and LOTR came out, Keefer did us all a huge favor with the rules for each.