Yes, this could very easily be done by editing the source code and compiling and building it. Of course there are 2 separate recruitment caps: the recruitment cap for people persuaded to join the LCS by talking about the issues or being liberated from oppression, and the recruitment cap for people who get seduced. There isn't any recruitment cap for people who get brainwashed. Anyway, as long as the recruitment cap is a greater number than the number of recruits of that type, you can recruit more people. So if, for instance, the function to return the number of possible recruits returns a value equal to the current number of recruits plus one, then you'd be able to recruit unlimited numbers of people, and that is only a very minor code modification. Of course, since your hypothetical mod would only take effect with 1000 Juice, the functions for the number of possible recruits would have if...else statements in them to see if you have 1000 Juice, and use the existing code, inside braces, if there's less than 1000 Juice, and return the current number of recruits plus one if you have 1000 Juice.
Oh yeah, and the functions to edit are all in /trunk/src/common/commonactions.cpp. The 4 functions to edit are maxsubordinates(), subordinatesleft(), loveslaves(), and loveslavesleft(), all in that file. I won't actually write the code for those functions for your mod... that oughta be enough information for you to figure out the rest of how to implement it. Oh yeah, and when you do the juice check, you do it with cr.juice, since those functions all have cr as the Creature variable, and juice is a variable that is part of the Creature class. Like, you'd say "if(cr.juce==1000) { code for unlimited recruits } else { original code for the function }". Or you could do it in the other order: "if(cr.juce!=1000) { original code for the function } else { code for unlimited recruits }". Either way would work. And I'd do that in all 4 of those functions. Well technically you only need to do it in maxsubordinates() and loveslaves(), since if you use the suggestion of the formula (current number of recruits + 1) for number of possible recruits, that'll mean that subordinatesleft() and loveslavesleft() wouldn't have to be modified at all if you did a good enough job on editing maxsubordinates() and loveslaves(). So really you only need to modify 2 functions.