by too hard, I would say do it completely in software, and no hardware required.  I don't know how difficult that would be.

Personally, 20MHZ would be okay, but 50MHZ would be awesome!

Vote changed to the 3rd option.

Yeah, personally, I'm for making a working version right now.  Maybe start with the z80, since more people know about it.

I don't think we should do a touchscreen

Great. But you only signed up to wikidot. I invited you to the site itself.  Be sure to change your tags to signify what team(s) you are on.

Recently, we made a wikidot site called otcalc.  It can be found here.  This is an amazing site.  It's all navigated via the top menu bar.  If you want to join, hover over the users button, and then click "Join".  That page will tell how you join.  You should get a wikidot account first, but for the life of me, I can't remember how.  I think it's mostly automatic, now.

If you hover over the users button, you can click on a button that says teams.  Click on it.  Most likely, you will not be part of a team, just yet.  If you are not a part of a team, and want to be, click on the "users" button.  If you are not in that last, It means I haven't added you yet.  Wait patiently until I do.  When I do, You will have a members page.  Click on the link for your members page, next to your user name to see it.  You can edit it to reflect interests, hobbies, or whatever.  If you click tags, you can do a space separated list of the teams you are on.  For example, If I was on all the teams, I would have:
admin z80-software z80-hardware arm-software arm-hardware.

Me and Albert H are the only two admins.  I will detail more things later, but for now, sign up and try it out!

[EDIT] More added:
Okay, so all the discussions should happen on Omnimaga, except a few things.  One of those are suggestions.  Suggestions are rather simple.  All you have to do is hover over the processor of your choice in the menu bar, eg Z80 or ARM, and select Suggestions.  Here you will see, if there are any present, the suggestions that people have given.  Creating your own is simple.  Just give it a name to identify it, and click "Create Suggestion".  After that, you will be brought to a page where you can suggest things or ideas like keyboard layouts, etc.  This is for both hardware and software.  You can rate these ideas up, or down, depending on whether you like them.  If suggestions are liked, then they can be accepted, or if they are disliked, they can be rejected. (Note: The automatic support for this is not done. I'm working on it)

Most of you probably want to change your buddy icon (Avatar).  In the top right corner, click on my Account.  Then, on the left, click "My profile".  Click "My buddy icon", and change it using that.

Do not edit pages unless you have permission to.  Eg, if you created the suggestion, you are the head of one of the teams and are updating the main hardware/software page, you are an admin or moderator, or if you are editing YOUR user page.  Tags are used somewhat in the site as described above.  They help identify what team you are on.  Please use them.  Note, adding the "admin" tag does not make you an admin.  You can also discuss pages if you want.  All these options are at the bar at the bottom right of the webpage.

Any questions are to be asked here in this forum.  Most of the discussion will go on here.  The wikidot site is basically a repository of ideas and information.  When we finish, the site will probably host all the information about the calcs, if we choose to make it FOSS.

Create a wikidot account here, and then sign up to my site here.  The forum for that site is the per page discussions, but there is a button for recent-posts under users in the menu bar.

Any questions?

I think that the +*-/ column should be to the right of the numbers.  Also, I don't think there should be a store.  Maybe if they all were free. Money is going to be complicated as it is.

Maybe have ok ret become left and right click for arm as well as ret.

Big thanks to DJ for setting up all the forums and sub-forums.  There are subforums for the hardware, software and progress for both the ARM and Z80 processors, along with a generic sub-forum for things like this thread.

Thank you, DJ.

As for the wikidot site, it is now open.  Access it at otcalc.wikidot.com.  Note: Development on the site is still in progress.  The discussion forums for otcalc on omnimaga are for main discussion, while this wiki is here to collectively store files, diagrams, suggestions and information pertaining to the calculator.  All wikidot pages should be editable by members, and can be discussed by clicking the "discuss" button at the bottom.  Oh, and please, don't mess with editing the pages right now, as they are not complete.  Also, the them is just a basic them I chose to work with.  It is subject to change.

Again, Thanks DJ.