OK, I guess I have to give a little more info.
I started out with making a requirement list as follows:
1 - The new item shall be exchangeable with the "old" one.
2 - Both items shall be possible to use.
3 - Minimal alteration to the existing tailstock is preferable.
4 - It must be possible to make the new item using a mini lathe and a mini mill.
5 - No exclusive materials shall be used
6 - The new item shall be designed as simply as possible.
7 - It must be easy to change between the two items.
This means that I donīt want to discard the original screw-feed attachment, but rather get more possibilities by adding the new one. I started out by thinking of how I could get access to the existing quill from behind with something else than the hand-wheel and the screw. Then if it was possible to replace what was removed to make the "old" item a complete exchangeable unit easily removed or secured.
What came up was as follows:

The first problem is to solve how to create the access to the quill and still not ruin the whole thing. It turned out that the end of the tailstock at (A) have a thicker end wall - a little less than 12 mm (1/2") - there are three holes, two for securing the visible thick washer locking the feed screw in place and one for the feed screw itself.
Now, if I drilled/bored out the wall and replaced it with a suitable thick "washer" or end replacement block (B) then I could re-use all the items as today at (C). Using two screws from either top/bottom or from the sides it should be possible to lock the whole thing securely in place. It could actually work.
But how does it look for a rack feed then? I re-drew the stuff to get an idea of how the rack feed housing could be fitted using the same manner of fitting.

Provided that the rack is not larger in diameter than 20 mm and uses a suitable DP or Module it should actually be feasible. The star-wheel block is just a sketch so far.
How large is the car steering rack from the Citroen? I have a scrap merchant fairly close and if I could get a used steering rack that would solve some machining I am not confident with.
Well, then came the question about the position of the star-wheel housing and which way the wheel should be rotated to feed the rack to the left (seen from the user perspective).

The difference in position can gain around 50 mm (2") back to front depending och choice. Then came the question at what angle to place the rotational axle of the star-wheel, vertical, horizontal, or in between? With the right choice the new rather larger "handle" will still not be in the way when manoevering other controls on the machine.
If we look at the different positions from the tailstock towards the headstock it looks as follows:

I would say that it is possible to put on the same amount of force regardless of position, it is more important that the handles does not foul (not faul as I have written in the picture ) any other control or get in the way of work or man.
I think I have to make some assumptions and a mock-up to get another step forward, meanwhile any comments are very valuable as I am not a machinist by trade and hence donīt have that hands-on experience. (My "trade is software, information and information systems.)
I hope that I didnīt scare you off
BR
/Peter