We don't see them because they're not cost-effective, not because they're expensive - there's an important distinction there. You could definitely give them an upgrade that cost points, but made them worth the cost.
For an unreasonable example:
[system]: E-wing only. When defending, you may cancel enemy [hits] and [crits] with your [blank] results. 1 point.
Now there's an upgrade I would buy, and would make E-wings very competitive, I suspect. And it still cost me 1 point.
Also, ships don't need a 'title slot' to take titles. Any ship can take titles, in the same way any ship can take modification upgrades. There is no 'title slot'.
The cost-effectiveness of something is pretty much based on how expensive that thing is to start with. As for a title slot; there are only a few examples out there that can take a title without giving something else up; amongst others the Tie Advanced, StarViper, YT-1300 and the YT-2400.
Title slot may not be the correct name for it, but any other ship that doesn't come with a title card in the expansion pack, pays for it by losing one of their other slots.
Cheers
Baaa
