the rumors ive heard is that so much of a percentage of your army MUST be characters, so in snese of realism 10,000 men would not be lead by 1 guy itd be between 5 or so...
the "must" factor is just a rumor i read, but its not as bad to army choices as saying "you have only 10% of your army to spend on characters" because, yes the fewer character armies would need to spend more points on characters, but its getting people to try new characters and the many character armies wont even care.
i think fantasy would get away with this much more easily than 40k though...