I've been having some decent achievements following the centrist path. Although maybe more centre-left. I should have made some screenshots or documented the exact steps I took. Anyway, I started with leftist Agri and Internal ministers, a right-wing Foreign minister, and a centrist Defence minister.
I used to know this but I had forgotten about it: the most important thing to do is avoid elections, while still keeping everyone happy. It's a difficult balancing act. The moment you call elections, the two wings of the military will go apeshit on each other no matter what else you do to balance them, and the wing you've supported the most will win out. Useful if you want to follow a left-wing or right-wing path, but not if you want to maintain a balancing act. Besides, if you get involved in a civil war, your military expenses will go up hugely.
To keep everyone happy, you MUST go through with the leftist land reform, price controls and food subsidies all the way, with a commie agriculture minister so that you don't get fucked by emergency events where the centrists will cuck out on it or the right will destroy it. At first the food subsidies will cost money, but if you follow the event chain, eventually you'll bring in ration cards and technical support for cooperatives, so the money spent on food subsidies will stabilise. Otherwise the leftists will always coup you I think. I was able to get the leftist commander Correa to pacify the countryside and outlaw the death squads (although some commies still got helicopter rides before that), while also still keeping the right-wing commander on board, with massive US military aid no less. I think this was more thanks to not having elections and can be considered a bug or omission perhaps.
To keep the middle class happy (although they can't coup you), you can follow their path for splitting up the dictator's estates and generally being nice to the small- to mid-sized coffee planters. This (along with the technical support to land reform) will give you some hard currency to finance health and education (but don't increase spending again afterwards). Although the game started complaining about mounting debt in the end, in fact the reserve currency went higher than the debt in the relevant graph, which I normally don't achieve.
Counter-intuitively, increasing spending on infrastructure doesn't seem to help much. I kept doing this in previous games, but this set of ministers never have it on their agenda, and I couldn't get any encounters to do something about this issue. It doesn't seem to matter as much as other stimulus for coffee growers. Cotton always seems to disappoint, not sure what's up with that or if the developers ever worked it out. Or if it's supposed to be some anti-capitalist statement by the developers.
To appease the right-wing, I kept national bank loans firmly aimed at producers of export crops, which is also good for your budget. The leftists will whine but they don't take action as long as you go through with land reform. I also kept a pro-US diplomatic line, including letting them deal with the military directly to avoid that whole stupid back-and-forth, so they will take care of your military expenditure. At the same time, I kept limited economic aid from the USSR/Cuba by going behind the foreign minster's back. There is a kind of glitch/omission here: even though the US will funnel endless money into your military, they will only ever give limited economic aid because you have leftist land reform and are doing business with the commie countries. You'll never get more than "apologies" from the US ambassador after that. But they still take care of your military bill, so it's all good. The lack of a civil war means no cuts in subsidies from the Eurofags and loads of that sweet IMF debt slavery. In the final year, most domestic events simply repeat themselves, so I used the opportunity to take some anti-communist positions in the UN.
The final verdict of this game acknowledged that I successfully held the centre ground and empowered small-size land owners. It also credits me for giving technical support to the farmers' cooperatives, so that the land reform did not harm exports. It claims that "the peasants were unable to grow enough food", but the graph in the game itself showed malnutrition going way down so I don't know what's up with that. Probably another limitation (it's a game from 1988, after all!). The final verdict also credited the health and literacy achievements and maintaining a minimum wage and allowing unions to organise (although I didn't indulge them further than that). It also mentioned the growing debt and lack of infra investments.
Given the deliberate difficulty of the game and there not being a real win state, I consider this one of the best results possible. Guess land reform really does kinda matter in a shithole banana republic where the webbed-toed incestuous land owners ran everything first.