eastbayarb,
I did a couple searches myself just to see what people had said in the past on this topic, and admittedly I didn't read through every message my searches returned, but I didn't readily find what I was looking for with "control without keyboard" or "control with joysticks and buttons". So although I'm sure it's been answered before, I'm gonna throw my 2 cents into the mix.

Use XP. With two joysticks, six buttons per player, Payer 1 and Player 2 start buttons, and a programmable keyboard encoder with a shift function (IPac, KeyWiz, etc), there should be no need for a keyboard. And with a trackball and a dedicated button or two for mouse-clicks, you can in fact control your entire machine without using a keyboard or a mouse - Windows, your front-end, your emulators, and of course your games.
One spoiler to this is if you need to run computer games (C64, Amiga, ST, AppleIIe, what have you), which are not arcade-style games. For example, if you want to run Bard's Tale III - Thief of Fate on your C64 emulator, you need to be able to type in the names of the spells you want to cast. So unless you want to get REALLY SLICK and have a hotkey set up to bring up a virtual keyboard, you're stuck with a keyboard. With that said, you can still play the majority of computer games by mapping shifted values (via your encoder again) for "Y", "N", the numbers 1 - 9, and some of the Function keys (F1 - F12).
Beyond that, here are some tips.
* As efjayel said, add your front-end to your Startup folder to launch automatically.
* As efjayel also said, choose a front-end which can shut down your machine automatically upon exit. Or this can still be done in a number of ways without a keyboard or mouse, that you can find with a search on this forum.
* Choose a front-end with a configurable control scheme, and remap the scroll, launch, switch menu, etc controls to your buttons and joysticks.
* Choose command-line based emulators which can accept parameters for full-screen, exit on escape, as well as the game name of course, straight from the front-end.
* Choose emulators with a configurable control scheme, OR those which conform to the default MAME control scheme already. Some emulators which are not MAME-friendly have been tweaked by third parties, do a Google search.
* Remember, to "Type OK" in MAME, just wiggle the Player 1 joystick Left then Right.
It requires some work and some customization, but in the end it's very satisfying to never have to roll out that keyboard hidden under the control panel like a dirty little secret

-EVE Games