I own two of the ArcadeSD's and one of the original ArcadeShop board. Also, I've built a few 48/60 in 1's for people as well have many different joysticks in various machines and have tried multiple variations of switchable joysticks.
In summary, IMHO, the only joysticks that will even feel / work right like a classic are those with a switchable Diamond/Square restrictor. Anything else simply will not feel/work right. (Though admitedly, I have not tried a 49-way yet but that is basically a square restrictor all the time)
I tried bottom switchable joysticks (J-Stick from Ultimarc IIRC). Work well but over time the screws can tighten or loosen and need adjusting. Plus you need access to the underside of the control panel through a coin door so won't work on coin-door-less builds. They are meant only for adults, you won't want a child reaching in getting cut on sharp edges or pulling off wiring (or reaching for more dangerous things away from the control panel). Completely hidden and people other than yourself will likely always forget and won't switch it.
I also tried the top-switchable Mag Stick from Ultimarc. It is very similar to the J-Stick and over time can have losening issues (quickly fixable). It only requires you to pull up on the stick and twist it 1/8th of a turn left or right to switch. Like the J-Stick it's almost "too hidden" and other people forget the rules of changing it and then complain it doesn't work right. Also since it uses a magnet to center instead of springs or rubber gromet, it doesn't have as much tension and has a hugely short throw. Like the J-stick it is microswitched based and noisy, though with any microswitch you can replace with the leaf switch to microswitch adaptors sold seprately to bring it closer to authentic classic.
One I haven't tried is the top-switchable stick (Groovy Game Gear though has been sold out for a long time). It will be similar to the above but is much more noticeable (good for new users, bad for asthetics). It has a lever exposed that moves the restrictor the 45 degrees need. Unfortunately it needs a large exposed square plate on top (much like a trackball mount).
I also have tried the rarer and expensive Suzo hall-effect joysticks. They have a dial on them that sets the sensitivity between 4 and 8 way. You could ideally set it to be perfect for one way, then wire in a switch to short it out to switch it to the opposite way (since it is not designed as a switch-on-the-fly). However this is all electronic--it does nothing to restrict the corners physically. In fact, the restrictor is always a 8 point star pattern -- very similar to a Nintendo 8 way restrictor, but a bit more 'sharp'. Therefore there is no easy way to slide from one direction to another.
The final way I have done for someone with a 48 was to find a Happ Ultimate? joystick that had the right combination of wear and spring and what not that caused it to hit the 4 primaries with ease but took a bit of work to hit the corners.. They could be hit, but you needed to think about it and press a bit more in the corner. This allowed them to do 4 way games easily but still manage to use it for 8 ways like Time Pilot/Scramble/Super Cobra and make them possible to play. I think with a Happ Super you could also bend the actuators a bit and control the amount of pressure it would take in a corner.
Honestly, there will be nothing better than a switchable panel or side-by side mounts of either a Bally/Midway 4 and 8 way or Wico 4 and 8 way leaf sticks. You won't get the same feel out of any other switchable or "ease" in switching.
Or, just buy 4 ArcadeSD's and put one of each in 4 cabs, restrict two cabs to vertical, 2 to horizontal and then 1 of each to 4 way and 1 of each to 8 way. Then there is no confusion in what mode to be in for each game.