The trouble here is that if you have been hacked, by definition something has happened to compromise the security of your computer. Thus, you're already in a flaky situation. If you could create such a system, that new system would just become a target for hackers - after all, if I can pull off a hack and leave the new digital tamperproof seal in place, wouldn't that be the best hack ever?
Worse, the number one (by far) best way to hack a computer is to get the user to do something stupid. MOST hacks are because a user clicked on something the system warned them they shouldn't click. And people do it anyway. So, the number one security vulnerability in any computing system is the user.
But the best news is that hiding tracing of how a hack happened is really, really, hard - nearly impossible hard. Which is why computer forensics is a thing. As always, as a victim, your best bet is going to be to get a good lawyer. And a hire a forensics expert.
Are you sure this is a technology problem? I agree that any technology platform is going to favor whoever is paying for the technology. So I agree that the big data companies aren't your friends in this regard. On the other side, the decision about what color dress to wear today is a very insightful one to consider. Since how we dress affects our self-image and our emotional state, and it depends at least partially on weather, culture, social status, tasks to be done today, expectations of who we meet today, what we want out of those meetings, and many more things, it's a hard problem, probably too hard to technology. Tech can't know that you're feeling a tad self-ware today, and so you need to wear that power-suit that got you compliments that one day last month.
Instead, I think this problem is one of personal cognitive load and attention budgeting. These are nicely addressed by various philosophies and lifestyle choices (think Buddhism, Danish Hygge, Ancient Greek Stoicism, the modern Simplicity Movement as just some examples).
I see the problem you're describing and I agree it would be a good problem to solve. Here's the problem: The size tools compress to isn't arbitrary - it's based on the algorithm, how compressible the data is, and how much loss of quality the user is willing to accept. The algorithm is generally fixed - as a user you just use the algorithm of the tool you're using (or file type). The compressibility of the data is defined by the data you're using. A bland picture with few colors is more compressible than a very rich one, for example. Acceptable quality is a bit fuzzy, and this is where the problem is. For an image, is cropping better than losing color depth? Or resolution? Are you concerned about image scaling - how it looks on an iPad vs a big PC gaming monitor? So, the problem you want to solve requires lots of input from the user, about topics the user either cares not a whit about (until the picture comes out bad) OR the user cares passionately, and is already using something like Photoshop or GIMP and doesn't mind the extra work.
I think this is a great idea, but history suggests it won't work like you might think. First, in the US a couple of decades ago, there was a big push for "generic" products, mostly in grocery stores. Food items were labelled with simple black and white labels and offered at a lower cost than brand name products. That idea lasted only a few years and died out. Also in the US, most grocery chains have "store brands" - effectively brands with no or little marketing, offered at lower cost. Has been moderately successful.
But I think you're discounting the value of a brand. Some brands are utterly meaningless, but a good brand has real value. Consider Toyota (reliable cars), or Disney (wholesome entertainment), or Levi's (quality jeans) or Coca-cola (consistent product worldwide). Brands are also a channel of accountability for consumers. I know Toyota stands behind their warranty, so I feel good about buying their cars. If I buy a Coke, I know what I'm buying. I might suggest reading up about brands - before your idea can take off, I think you need to be able to address the gaps you'll have by not having brands.
As a former software architect and manager of software development teams, the danger here is that so much "new skills" work needs to be re-worked. It's the re-work that gets expensive for big organizations. Worse, every big org I worked for had tons of people already working for them trying to make a break into IT - imagine the proverbial kid in the mailroom who just finished his college degree or some certification program and wants to work in IT now that he has training. Plus, we tend not to learn from doing - we learn from getting feedback on what we did. Giving that feedback means that, by definition, your "new skills" work costs the time of someone to give feedback, and then potentially re-do the work you just did. When training up an employee to stay with the company, this is a good investment. But if you aren't sticking around, why should I invest in you?
That being said, if you are in the US, check out https://givecamp.org/. It's exactly what you suggest - people doing work for small non-profits for free. I helped set up a chapter. But the trick is we always built teams of people - some senior, some junior - so the non-profit got something that was good. I'll also second another comment - learn about GitHub and FOSS.
Most large, reputable news agencies do this through an older technology - radio. NPR and BBC World Service still do top-of-the-hour news summaries, less than 5 minutes in length, and available on-demand on their web sites. This used to be a standard feature of any new radio service in the US. You got a summary of the news at the top and bottom of every hour. NPR (US), BBC World Service, PBS (US), and many newspapers do these still today,. Some post them on their web sites, some publish as podcasts. All use professional journalists with high editorial standards. What is it about those that you find inadequate? The New York Times calls theirs "the Daily". NPR does a four and a half minute summary of news every hour, available in their website.