That might limit number of units in the field but the tactics won't change at all, considering little has changed in decades.
The production of the Merkava tank was halted due to a change in tactics -The MBT was only useful on a conventional battlefield and suffered fighting insurgencies. Tactics dictated production.
But the SLDF officers are have to rely on the old tactics until they replace most of their Merkava to the newer one, or do their best to make the makeshift tactics with these outdated machines. And you know, the new production costs not so insignificant time. Before then, all the frontline units can do is just utilize what they have as best as possible.
The change of meta calls for the change of production, of course, but still the production matters in the reality because it determines what you actually have. On a computer game, you simply put what you want without such matters. On a RPG, the game master can rules what you have so at least the initial spend is not so problematic depend on your persuade skill. But even on there, there are the concept of limiting resource. And you can't set each person/faction's assets as you want in the reality.
Seriously, you can't use the cavalry tactics without a cavalryman or a horse(or its equivalence). That's why Aztecs were not using the cavalry for century, and many nations on the history are short on cavalry, for example. They don't use cavalry much because they thinks that infantry is far better. Actually it's half correct - infantry is actually far better, not for their sheer prowess, but the cheaper cost to make up the difference. So the truth is, they CANNOT use massive cavalry.
It is not a secret that only a handful of elite cavalry units are able to decimate the infantry units that far outnumbers them in the pre-modern era, and the history proves it. But in the reality, almost all nations of the era were still utilize the massive number of infantry, despite of the fact that a cavalry is worth a dozen of infantry or more. I remember that only the modern times(around 18th to 19th) cavalry have very high percent in the army of western europe, despite horse is still not so cheap to get(and you can't acquire them so fast either).
Yes, there are some specialized job that is not so easy on horseback. But it is not the only reason. it is because the most nations are not able to afford enough horse and train such a massive number of cavalryman. Only the nomadic nations are possible to do, for they are have to learn the riding skills and hunting, which is essential to cavalry. But the rest of them are not able to afford such expense.
Also, even if you want to have a battalion size of brand new M1 Abrams, if all you can pay for and/or access for the market is a battalion size of M4 Medium Tank, it just results you to have a battalion of M4 Medium Tank. I think that it is nothing wrong to replace M1 Abrams to heavy/assault(or even medium) mech and replace M4 Medium Tank to bad light mech.
And, speaking of horse, although there are very niche area that horse is actually better than the car, but the concept of real 'horseback rider' is virtually extinct in the militaries of our era. However, if you are a local militia commander, and can't buy even a jeep, but you can buy(or already have) a bunch of horse, all you can do is utilize the horse, not the tank tactics.
Remember, all you can got is all you can use.