Out of curiosity why do you think 1e is a good jumping off point? Or a good model to emulate? The Rules Cyclopaedia, yes. But 1e is bulky enough that as far as I know no one ever plays it using all the rules as written - and has a nasty habit of squirreling away rules on obscure pages of the DMG so almost no one actually knows what the rules as written are. It's also awkward and inconsistent with such artifacts as Percentile Strength.
The first rule for the basis for a game should, in my opinion, be that the rules should be simple enough, clear enough, and unambiguous enough that the game works. We're talking Red Box not AD&D. And then there should be a chapter talking about house rules on top of this.
So why 1e? I just don't understand the love for it.
Simply put, because the Red Box is too simple, while (pre-UA) 1e already bakes in a lot of the relatively basic changes I'd add:
- class divorced from race - an Elf can be various classes, etc.
- more classes to support more archetypes
- all the levels of the game are there; where Red Box only has the low ones and BECMI splits them up.*
- a wider variety of spells, weapons, etc.
* - I can't speak to Rules Compendium at all as I don't own it and in fact have never even laid eyes on it.
From this jumping-off pont it's pretty easy to strip out the uglier bits and simplify some of the rest:
- drop weapon speed and weapon vs. armour type
- drop the initiative system and replace with something dirt simple e.g. everyone rolls d6 each round, ties are allowed
- open up what races can be what classes, and how far they can advance (though keeping some restrictions to taste is fine too)
- drop the grappling rules and replace with...well, whatever you can dream up; they've never been done right yet
- (personal peeve) drop psyonics
- streamline the combat matrix somewhat
- give monsters the benefits they'd get from their stats e.g. hit/damage from strength, h.p. from con, etc.
- organize the books better, failing that at least provide a good index
But keep the overall philosophies:
- the DM worries about most of the mechanics while the players worry about the exploration, story, and characterizations
- the game-as-designed starts out somewhat gritty and evolves into heroic fantasy as it goes along (obviously this can be changed to suit each table)
- the math is loose enough that a bit of messing with the system doesn't break the game
- character archetypes are well supported
- magic isn't always the answer, it's risky and easily interrupted
- the concept of character build a la 3e/4e is almost nonexistent
- multiclassing is disadvantageous
- characters are usually simple enough that playing more than one at a time is easily possible if one wants
- character generation is relatively easy
- level advancement is a result of play rather than the reason for it
- the general feel is open-ended and somewhat random rather than pre-packaged
- guidelines, not rules
There are some very elegant mechanics in 1e that have been lost - cleric-vs.-undead turning matrix, resurrection and system shock survival rolls, teleport has risks, polymorph self has limits and poly. other is always unwelcome, revival from death costs you a con. point meaning death (usually) has permanent consequences, etc., etc.
I'd be tempted to use 2e as a jumping-off point instead except that at release it was missing too many things (lots of classes weren't there, all the evil was stripped out, etc.) and later on it became too bloated and unwieldy.
Not the most coherent answer, I realize, but it's a start.
Lanefan