Multiple directions of the company: one site, subdomains or different sites?

Question

Search Engine Optimization

Good afternoon!
I will describe my situation/SEO-task. Some company A has a website siteA.com. The site is soon 2 years old , relatively young, search positions are so-so (although there are several queries in the TOP10, but this is not enough compared to the whole set of queries). Optimization is also not so hot. There are many errors, but it did not seem to fall under the filters, there are many pages in the index.
Company A is active in many areas . All these directions could be globally divided into 2 large classes. Like, for example, humanoid robots and satellites. Two practically non-intersecting directions. Is that the materials for production in some places may coincide. Not the point. Various.
Plus, in each of these classes there are still different directions. For example, you can sell processors for robots, of which there can be a lot of brands. And you can, for example, engage in hydraulics for motor limbs. The directions, as you know, are very different, but both refer to humanoid robots. Everything is the same with satellites, you can supply solar panels and batteries, or you can supply engines for rockets that these satellites deliver into orbit. The differences are also strong, but everything belongs to the class of satellites. And of course, again, brands-brands-brands.
And company A does all this, and supplies hydraulics to various manufacturers of robots and processors, and maybe even conveyors for assembling robots .. Plus, rocket engines for launching satellites, solar panels for satellites, and other spare parts for satellites. Yes, and different satellites. For television, for surveillance, for Hubble telescopes and for a pulse gun that destroys meteorites. Almost skynet. But not the point.
The question is, what is the best way to remake the site from the point of view of promoting this company :

1. One site with many subsections. As it already is now, just remake it globally (make a new site in fact), fix all the errors, carry out full optimization and engage in its global promotion in all directions.
   
2. Subdomains. There is already siteA.com. We do not touch it yet, select a priority direction (or 2-3), make a sub-site (s) purely in this (their) direction (s) processor-robot.siteA.com, optimize, promote, simultaneously deal with the following areas (less priority), and so along the chain until we implement all the directions, at the end (or earlier, I don’t know how better) we change siteA.com itself and “close” this entire chain. On siteA.com general information about all directions, brief information about the company, press center and more. Everything is done in approximately the same general style, but each direction has its own unique features: the design is slightly different in places (but not the general concept), of course, completely unique content, its own news and articles.
   
3. We divide only two main classes into subdomains: robots.siteA.com and sputik.siteA.com. Everything else is the same as point 2. Will there be any difficulties in promoting here, because there are processors for robots, and hydraulics, and a conveyor belt and much more, quite different topics in terms of promotion, but in general, one common theme? Wouldn't this be a semi-solution compared to point 2?
   
4. Make generally different sites but all under the same brand with similar design elements with the same logo and other things. Maybe it will be good for promotion, but will it be good and convenient for the end client of company A, because everything is not centralized, scattered across completely different sites, there is no overall picture, and I’m silent about the fact that there may be certain large clients who you need to launch a satellite and put a robot in it. Or a better example: to buy processors for robots and install a conveyor belt for the robot's system unit.
   

Perhaps the example is rather comical, but I tried to describe the real situation as clearly as possible using an unrealistic example.
I am also well aware that similar topics have already flashed and I have already read a lot of things and even listened to a webinar on this topic. But he never answered his own questions. Each case was individual and I could not fully compare it with my own 100%. Everyone has different inputs.
I almost forgot to outline the goals:
1) You need to successfully promote the site in the TOP10 / TOP5, for a huge number of keywords in all areas.
2) There is a budget, but no one will scatter it without very significant and justified reasons from all sides .
Therefore, the path must be 100% working with prospects for the future and at the same time optimal. As they say "necessary and sufficient".
PS I also looked at various successful examples, such as Yandex, Vikimart, Drom.ru, Avito and many others. Even among them there is no single solution. Avito goes the first way, core the second and so on. Where is the truth?
PSS
I would like to hear the opinion of a practitioner, without guesswork and theories.

Answer 1

Each subdomain must be rotated separately.
If not a lot of information is supplied and does not dazzle the eye, then everything is on one site - definitely!
on one domain - there will be a lot of things for the search engine to catch on, + less effort and money to promote other subdomains / sites. In the future, you can then relink with other domains ... something like this