Having the 10% rebuy cost detracts from gameplay since it takes away flexibility in outfitting. No longer will players try different settings on their vessel when modules are expensive. In return you get a little bit of gameplay back in the form of cost management. I rank trying out different setups a lot higher in enjoyable gameplay than an added cost management feature.
Have to disagree there. Swapping modules is very different from gameplay in the Elite: Dangerous sense of the word. The game is about mining / trading / exploring, as it is obviously not a "swap my modules game". If ppl want to experiment with modules, the best thing, is to do so with low end modules, there's a small cost (with the 10%) but it's small on low values. If you like the module .. upgrade it to an A5.
Yes, it's fun to experiment with and work module performances out but that's only fun the once. Longevity type fun only really happens once you take a risk with the credits it took you effort to earn, apply it to modules with a now inherent value, and take your ship out into the galaxy at large no? (hoping you don't run out of jump range with a pirate on your tail for eg.) The alternative, allowing you to test drive, permanently, is a bit dull imo.