There would have to be some mechanism to prevent bots from creating tons of free generals though, as has already keen mentioned. Maybe only a single free general could operate from an IP address, or one general per range of IPs. This world still probably be much to easy to spam...
If free hunters can do very little things, i don't think would be a problem, even because running lot of bots require anyway some hardware for that and if income is ~0 than there is no interest in creating them.
I think that a way to focus on few hunters is to implement more in depth the RPG concept of the game, i mean the fact that a hunter never die really, so you can register a name for the lifetime and just "revive" him (technically his address) whenever he "dies", and keep improving his stats and at that point we can do the opposite: making a new hunter costs you "a lot", but revive him doesn't (but every time hunter dies means that the hunter lose some stats like attack power and carrying capacity), so a player can invest for entering the game and then improve his hunter(s)
of course this is something that need to be thought deeply but i think it could works.
Another interesting thing could be that a free game could be on an alternative net (not testnet that's for test, but we could have a "playgroundnet" that runs on his own blockchain and reset every 7 days or so, this way new players can train on that net (and we could use that even for experimenting new things).
this special playgroundnet could be done premining most of the coins and distributing them to lot of address that could be claimed by anyone, could even be a centralized server since there is no exchange/money value linked to it, but at least could be useful for players that want to understand the game, and for mass testing purpose