We're always glad to accept suggestions for desired new features; you can search the forum for the keyword "wishlist" to get an idea of what others have requested that we've already logged for consideration as possible new features and improvements, and that's just here in the public forum, with many more such requests via email to Support also having been logged.
We're well aware of the desirability, appeal, and utility of improvements such as support for additional payment processors, so bear in mind we're not stonewalling or refusing anything here out of sheer stubbornness or anything like that. We really do want to deliver the improvements that most of our clientele want and would benefit from, but we're also not a bespoke development shop that can jump on any client's request instantly; we have to follow a coherent, internal strategy that takes our entire system, user base, and market niche into consideration. Knowing what our clientele wants is one thing; being able to actually implement it, and exactly how, is another matter entirely.
Fiscally speaking, our revenue goes almost entirely towards covering our costs to operate the service itself and ensuring that it will remain reliable, stable, and fully operational into the foreseeable future. There isn't much surplus that could be reinvested to hire and train additional developers, so we have to make best, most efficient use of the existing staff and man-hours at our disposal that our current revenue can already sustain. Increasing revenue means increasing our subscriber base, which depends on offering more and better features, so there's a bit of an inherent catch-22 there.
Technically speaking, many desirable (and tentatively planned) new features and functionalities are simply "backed up behind the dam" of our current Flash-based Seller Admin, which by now has simply become too complex and crufty to modify readily without breaking it in unexpected ways. We've been making what improvements we can in ways that don't require touching the Flash admin, under the hood and in non-Flash interface screens (e.g. uploader windows and log displays). However, adding any significant new functionality that requires a user-specific level of configuration and control in Admin itself is simply waiting on completion of a brand-new Admin built from scratch in DHTML, which has been Development's primary focus for some time now. I went into more detail about this challenging long-term project here: