...Jeremy simply needs to have his starting logistics reduced, leaving him with only one artillery unit (an advanced one, of course). It's hard to come up with anything more appropriate than that.

The option seemed decent. But the fact is that in such a situation, Jeremy will often become even more aggressive than he is now. Level 2 experience for artillery – and he can immediately break through anything. So, rather than doing that, as Dirty suggested, he should be left without artillery, replacing it with something else (for example, ranged attack). This would create a kind of Torosar from the Cove faction. The fact that he has an item worth 5K gold at the start is already overpowered.