From: Waipahu, Hawaii
I agree with Joram. If you are at war, or at risk of being at war any time soon, with a neighbor who can really hurt you, I wouldn't try this.
But, if you do want to try it, make sure you have plenty of trained draftees in your pool and that as many of your units as possible are either in a city or with a depot. Rotate them in and out if you have to.
It also seems to me that if you set your readiness to 50, your militia will also shrink and then consume some of the better replacements when you up it again. I don't know off hand if that will cause them to gain morale, or if they're stuck at 1.7; I've just never payed any attention to what happens when militia units are fleshed out with replacements. If they do go up some, that may be a waste of good troops, since militia are usually just garrisons for your cities. But, I guess if you want better milita units this may be a way to get them, if their morale does indeed go up like other units.
A lot to consider before doing this. But, give it a try and tell us what happens.
BJ- Just put your militia on 'forage' and they don't absorb any new recruits. AFAIK, militia are stuck, forever, at 1.70 morale.
Playing as Spain and Turkey, you can, pretty much, decline to make war for long enough to re-train your armies. Until you make yourself a target, by winning and garnering glory points, you're pretty much ignored, especially as Spain. Anyone that wants to jump immediately into battle should go with France, Russia, Austria, where they've got ready tools to work with.