Each modification that a pilot purchases will increase their reputation low-grade modifications provide a smaller reputation boost than high-grade modifications, and each reputation tier requires more and more reputation to progress.
Reputation is measured in 5 tiers, with tier 5 representing the maximum level. Upon unlocking the services of a ship-focused Engineer, a pilot can begin accruing reputation with that Engineer to unlock higher grades of modifications. For example, to gain access to Lori Jameson, a commander must first develop reputation with Elvira Martuuk to earn a referral to Marco Qwent, then develop reputation with Qwent to earn a referral to Jameson.
As commanders improve their reputation with these Engineers, they will unlock referrals to other, more selective Engineers who offer further sets of modifications. Initially, commanders are aware of a subset of Engineers from public knowledge. There are a total of 13 Engineers who specialise in pilot suit and handheld weapon modifications. There are a total of 25 Engineers who specialise in ship modifications. Once invited and having traveled to their workshop, an Engineer's services can be unlocked by completing an additional task, ranging from providing a specific item to turning in bounties. Be aware that attempting to land at a workshop without an invitation is treated as trespassing, and offenders will be immediately attacked by the workshop's defences. These requirements vary and some Engineers are easier to obtain an invite from than others. In order to obtain an invitation to an Engineer's workshop, their invite requirements (listed as "How to Get Invite" in table below) must first be met. Pilots will initially learn about some Engineers through rumors, but as they gain access to Engineers and build reputations, those Engineers will inform them of other Engineers with a wider variety of or more potent modifications.