I'm wondering whether your dilemma is perhaps the result of two problems, each of which can be tackled.
Have you researched what fascism actually means? Your description of the rebel country as "boasting a popular and charismatic leader [in] an authoritarian, fascist dictatorship, in which civil rights are suppressed somewhat and the state has most of the power" suggests that you're using the term quite loosely, perhaps based on popular (mis)conceptions.
Fascism is by definition "authoritarian" (= "dictatorship" and "state has most of the power") and anti-liberal (= civil rights suppressed). But "anti-liberal authoritarian dictatorship" also describes other totalitarian regimes (think modern China, North Korea, the old USSR, Cambodia under Pol Pot, or even religious totalitarian states in the Middle East). Why do you need to specify that the particular model is fascism? Are you simply combining "charismatic leader" with "dictatorship" and coming up with an image of Adolf Hitler?
This leads to the first problem: both you and your readers may be distracted by the leader and the risk of associating that leader with Hitler. This may be greatly limiting your ability to explore a more nuanced and intriguing scenario, and it is also likely to limit (or even destroy) your readers' willingness to accept the premise that this dictatorship is a justifiable solution.
Solution 1: ditch Hitler as your model (whether conscious or not) and consciously construct a different leader. Are they power-mad, or is their motive more altruistic? Are they the embodiment of Orwell's Big Brother, or more like the Philippines' tough leader Rodrigo Duterte, or the more ambiguous Trevor Goodchild, or even King Arthur? Does the leader enjoy mass popular support, or do they maintain power purely through military might? Do they have a clear and unshakable sense of mission (or even divine selection and duty), or do they have nagging doubts about their role?
Secondly, there's the issue of fascism itself. Since most readers will associate fascism with Nazi Germany, there will be a powerful antipathy towards anything you write that appears to offer a justification for fascism in your novel.
Are you sure you understand the difference between fascism and other political regimes? It may well be that your rebel country's government shares some elements with fascism: certainly the authoritarian control, and perhaps an ultranationalism rooted in romanticism and myths of superiority vs decline. On the other hand, your rebel country might not really be fascist at all: for example, is the dictatorship defined by its overt opposition to liberalism, communism and conservatism, or does it lack such a clear "negation" motive?
Let's say (for argument) that you do have a good understanding of what fascism really means, and you want to explore its underpinnings via your novel. The problem is that the more obvious the connection is between your rebel state and fascism, the more likely it is that your readers will demand that you portray this rebel state and its leadership entirely negatively.
Solution 2: Explore some of the fascist underpinnings of your rebel state but at the same time distance it from anything resembling Nazism. This is undoubtably tricky, but it's certainly possible.
For example, your state might have willingly accepted a wartime footing where every effort is towards the national defence: well, that could easily remind us of the state of affairs in the Allied countries in WWII. Political dissent is seen as unpatriotic, and the government legislates a Patriot Act. There are panels set up to root out unpatriotic dissenters (a la McCarthy era). But the state of emergency is deepening, and parliament has become paralysed: the only solution is to set aside the Constitution and reimpose strong law and order....
You can see how the above trajectory delivers the downfall (well, "temporary suspension") of democracy, without necessarily seeming like fascism. Indeed, there are plenty of examples in the last 30 years of democracies being suspended or elections becoming shams.
Fascism is deeply rooted in romanticism: a once mighty nation has run off the rails, and needs a firm hand to restore national pride and economic might. It's also deeply rooted in a belief in militarism or in the value of brute force, which can be closely connected to stereotypes of patriarchal power. You can look to explore these elements in a way that connects with more modern paradigms rather than harking back to Nazism.
Bottom line: fascism is popularly despised, so any exploration of its underpinnings will only be acceptable if you avoid any overt connection to it.