Better linux support is enough
As someone already tell it: the first thing you should do is to provide a better HW support. e.g., provide drivers for the kernel, so a developer could use it for his prefered distro. Or at least target Ubuntu, but for many of your machine. And all drivers etc are available in a repository for apt (and why not, for RPM etc), and updated for new versions of distros.
Don't target only one machine. For me, the XPS 13 machine doesn't fit my needs. I'm using a latitude e6520 (i7+8go+ssd 256). I'm a web developer but also a C++ developer. And probably this e6520 doesn't fit the needs of other developers. So try to provide drivers at least for one machine in each categories (xps, inspiron, latitude...).
I had bought a e6520 (one year ago), but unfortunately, it isn't supported at 100% by any linux distro:
- Optimus is not supported so only the nvidia card is used (and because of this missing feature, the intel card is not deactivated, although it is not used). So my battery life is tiny (2 hours, ouch). There is a project to support Optimus (Bumblebee), but it does not work very well (two weeks ago, I tried to install it, it crashes Ubuntu, X did'nt work any more etc, I had to reinstall the distro) and is not really friendly to use.
- The trackpad (multi-touch) is not supported too. It is seen by linux as a simple ps/2 mouse.
- The SD card reader and firewire didn't work at all.
- the suspend mode didn't work very well.
- the fingerprint reader doesn't work at all
I had to wait one year to see the SD Card reader, the firewire and the suspend mode to work out of the box into recent distro. Linux 3.3 seems to fix the support of the trackpad, but it is not yet into distros. For Optimus and the fingerprint reader, I'm still waiting... The support of Optimus, (so the support of hybrid graphics into linux), is a critical issue since the missing of this feature greatly reduces the life of batteries.
So, spend your energy in the linux support for many of your machine, instead of to target only one machine and only one category of developers with a single distro that will fit the needs of only a tiny percent of developers.
I don't think it is useful to preinstall bunch of developper tools, since each developer use different tools. For example, some of them prefer to use Eclipse, other only Komodo, or VIM etc... If you preinstall some tools, you could be sure that some of them will be useless for the developer, and some tools were missing. However, you could provide a software which will allow to choose and install easily different set of softwares. The user could choose between several sets of software, depending of its profiles. After selecting criterias, like "i'm a PHP developer", "I'm an Eclipse User", the software install the LAMP plateform, Eclipse and relating tools.
So, to summary, first of all, provide drivers at least for ubuntu, but for many of your machine. If you do this: the customer can choose the machine he prefers, and you can target not only developers, but also other kind of users. Doing a distro targeting developers with preinstalled software that the developer won't probably use, is useless. A developer is supposed to know how to install his prefered tools. But not the "lambda" user. So, for him, and for developers too, the distro (ubuntu), should work out of the box for the most possible dell machines. From my point of you, I don't care the tools you could provide. I want a laptop that works!