I ended running this last night for some folks from work and it went over pretty well. They get together infrequently. So, it was rather nice of them to be subjected to my expiraments.
Anywho, it worked. I can basically run more traditional DnD game (with short/long rests and all that jazz) using many of the mechanics from ICRPG.
The key was getting rid of stuff like bonus actions and proficiencies. No fighting styles or twf fights or whatever. I then folded in the abstracted movement and ICRPG target numbers. I also used ICRPG +d12 for crits.
The closest thing to proficiencies were class features of the rogue and scout. Which basically said stuff that rogues and scouts do are easier checks for them. Everyone understood. No need to spend time weighing animal handling against perception.
Spells were tricky. They had no descriptions - just a name. The player casted by rolling a d20 against the target number and a d12 for effect (doubled as d12 to determine mercurial failure in case of a 1). On success the spell goes off. With a roll of 9 or so on the d12, its about as peak effectiveness. Less than that, it is progressively weaker. Determined in the moment without complicated charts.
Clerics used DCC mounting disapproval rules. Cleared on long rest or by expending a hit die to pray on a short rest. Wizards could expend a hit die to boost the casting roll on a spell but must declare it before the roll. I will probably use hit die as the uniform resource for similar powers for other classes down the line. Since classes will cap out HP at level 3, no one will ever have more than 3 hit die. All get recouped on a long rest.
Armor and spells that gave armor were toned down. Light armor gave 1 ac (5 max dex). Medium armor gave 3 ac (3 max dex). Heavy armor gave 5 ac (1 max dex). Basically, dex+armor=6. Shields gave an extra 1 but only some folks could use them. Stuff gave less armor since enemies no longer benefitted from a proficiency bonus.
I experimented with the shattered shield rule and will keep it but only allow it once per short rest (players commented on abusive use cases).
The lack of initiative, by the way, was great. Highly recommend. Would do again.
Thats pretty much it. I will probably brew up a campaign using this.