Possible and pretty simple. To get an idea, read the pin coder test roms thread. They discuss how to make a 16x rom selector daughter board

Here's the problem with this idea.
In almost every case; the boards are already hard jumper-ed for the smallest supported EPROM size.

You have to physically reconfigure the board to use this larger multi-rom... most people wouldn't want to undertake that project just to get roms for multiple games in it because you can't use the other games with a different hardware configuration (playfield).

That said; I'm happy to be wrong.

That has been done like 20 years ago by a company named twobits.
Device was called fixit and it was a really neat board with lot of potential, however almost nobody has heard of it i think.
It was priced right at $70 but unfortunaly the owner would not ship to Europe otherwise i would have bought a dozen. I have bought one through ebay, and i have used it for years and love it.
2 or 3 years ago Twobits was sold to Gameboards usa, i inquired immediately with them and they ship to Europe but they raised the price to $120 which is too much i think for what it is.

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It had a nv ram on it, it was the first time i saw it mentioned in a pinball related item.
It was also very handy for using on mildly corroded boards, since you could skip the complete ram section of the cpu board so these parts could be removed. No jumpers change needed.As said, it was a very clever and convenient board.
I got a switch testboard with it as well on a seperate kit, if i remember correctly but i never really used that because i already have a bench tester.

Hm, $109 is still way more than the original $70 which i thought was ok.
For a bit more you have a complete repro board.

I have one of those & I had to get it via eaby too & use a parcel forwarding service to get it to Australia.

They are quite handy, I used it a few times.

Twobits were also the first to make the -35 repro MPUs I think, I have one of those MPUs as well.

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Here it is plugged into J5 in a working -17 mpu.
I switched the Fixit to test mode & the Fixit verified the RAM & ROMS were working. I removed a ROM & then the 5101 RAM & it failed the test on both. I really didn’t think these worked on a -17 as well as a -35 as pins 33 & 34 are not present on a -17. Seemed to work.
The available tests are for ROMS, RAM & the reset section only. Which typically covers most of the common faults with these MPUs.
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It seems much simpler to make a socket for the CPU than using U2, then you don't need to make any modifications for any boards.

Yes, main use really is to check & eliminate problems associated with the reset circuit, ROMS or ROM sockets on a locked board. Remembering the design of these boards are more than 20 years old, so I guess that's why the thing is so big.

With the cost of replacement boards it seems prohibitive. I like the weebly boards. Great customer service and reasonable. These old bally boards aee pretty old and often are unreliable due to alakaline issues.

U2/U6 only have a maximum of 12 address lines (A0-A11) going to them, making the maximum amount of Rom that can go there 4k. Any game that uses 3x2716, 2x2732, 4x2716 can't fit in a single rom that will also fit in u2/u6.

The processor chip U9 has all 16 address lines coming from it, so that socket can address the entire address range, but for stock roms you only use the signals A0-A11, A12, and A14.

The fixit is great, as long as J5 was in good shape you could get really roached boards back up and running for $70.

Personally I like to have the original ROMs on replacement MPUs. I actually avoid boards with DIP switch selection of the games whenever possible. Simple reason for this in there are a lot of update ROMs floating around with bug fixes, 7-digit displays, free play, etc that are not in the original ROMs.

Weebly has the variants in his combo rom, and is actively in touch with at least 2 of the people that actually write these roms (or have clearinghouses of the mods archived for inclusion)

Alltek refuses to add them although he does have some free play variants there (for bally) as well as (probably by mistake!) a couple of modified ones.

Awesome. Nice to know.

I think the U9 module eprom enable could be as simple as this. NAND chip 74HCT00 and you shouldnt need any pull up resistors on the daughter board.

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For the EPROM to make combining roms go in numeric U1, U2, U5, U6 order, EPROM typical A12 is wired to CPU A11 and EPROM A11 gets wired to CPU A14. /CE is grounded. Then wire up the rest of the address pins used typically on the MPU EPROM. The left over upper most address blocks route to a dip switch with pull up resistors so when the switch is closed that address is grounded. When the switch is open the address is pulled high. That will let you select 64K chunks of ROM in a bigger chip.

Build the 7400 NAND, EPROM socket, CPU socket, and dip switch on a proto board. Use socket mating headers to plug into the U9 socket.

ebay.com link: 10 pcs US 40 Pin Single Row 2 54mm Round Male Header M114 connector gold plated