Weekly vs. One-Time Payments
So as I finished watching the latest stream, Brad mentioned how cheap a particular mercenary ship was... and I tend to agree, mercenaries are relatively inexpensive.
When he mentioned that, though, for some reason, an idea came to mind that could make mercenaries much more interesting, at least in my opinion.
Instead of a one-time payment for a mercenary ship, why not have weekly payments to the mercenary? This would make it possible to lose a mercenary due to insufficient funds, and then the mercenary would go back on the market.
Another possibility would be for other factions to offer the mercenary a higher weekly rate. In such a case, the mercenary might ask you to increase weekly payments--and if you say no, then they'll fly away to their new client.
One other possibility that comes to mind would be a time-based contract similar to treaties. The one-time payment would become a fee for 25 weeks--or some other number--and at the end of the contract period, you'd be asked if you wished to renew the contract, which would require an additional payment.
If the devs are going to rebalance the costs of mercenaries anyway, maybe that's an opportunity to change how they're paid, too... just a thought.