Making them scarce only hurts the "Drucartan Heresy" players in that
it's less efficient to recruit with a big unit than many small ones.
But that may or may not remain true, and the Drucartan Heresy players
can easily afford to pay top dollar for new units anyway, monopolizing
the supply and screwing everyone else over.
Making new units "free" will not only cause problems like making
repeat suicide attacks very cheap and annoying, it makes the cost of
training people in various skills much less, because there's no
initial 500 gold to pay. Major changes like that to the system should
be considered with all of their ramifications first. It also will tend
to dramatically increase the number of units, making turns longer.
Nobody has commented on my limiting work time proposal yet. Does that
mean that you all agree, or that you think it's beneath comment? ;-)