The outcome should approximate the outcome of the full court proceeding.
Make the arbitration rulings appealable in court on the basis of factual errors, errors of law, corruption, and potential errors by omission (i.e. failure of discovery). And make the company responsible for the full costs of the litigation if the arbiter's judgement is overturned. And punish the arbiter, perhaps a 2 year ban on accepting any case from that industry.
I'm sure more adjustments would be needed, but it should be possible to get both the arbiters and the companies to want arbitration to be a faster, cheaper route to the same outcome as the courts, rather than a steamroller that avoids all accountability for the company.
That sounds like you want all the benefits of an actual court without all the costs of an actual court?
Barring that, faster and cheaper is better.
Simply limiting discovery, counterbalanced by loosened rules of evidence, followed by allowing specialist arbiters and avoiding the multi-year wait for a court proceeding seems to be faster and cheaper. There is a small error introduced by allowing discovery of 1,000 pages of emails instead of 100,000, and by allowing hearsay or affidavits, but probably most disputes would not strictly depend on deposing a dozen people and interpreting the 23rd box of company documents.
(Which isn’t to say I think the system as it is is good, just that there is a good)
Why do court cases take so long and suck up so many resources? Start with that. Perhaps reduce the amount of legislation/laws/etc. on the books, and write laws that limit the litigious society we find ourselves living in.
That is of course easier said than done, but we've chosen this path and can choose to unwind it if we have enough desire to.