Both games are looking good, Why did you stopped to develop games for z80 computers?
Thank you!
While both games received good reviews at the time, it is definitely Renegade and my 3rd Amstrad title,
Gryzor, that players still seem to have fond memories for all these decades later on.
I stopped developing for the Amstrad because the ST and Amiga were becoming popular (and cheap) enough that my company wanted me to switch over to those ... and I was quite happy to get to develop for the more-powerful machines.
If i may ask the sources, i would convert them to EP, the graphics can be stolen from the released game 
Yes, extracting the graphics from the existing game would be the way to go. I did that myself recently for one of my old Amiga/ST games.
However, I really can't see giving out old source just to have a game ported over as-is to the Enterprise without any significant changes.
If someone actually cared enough about the game, and about the Enterprise computer to go ahead and make some changes to improve it, either in terms of the game itself, or to take advantage of the Enterprise's unique capabilities, then that is more interesting.
For Short Circuit, that would probably be changing the game itself so that it gave the player more hints about what they need to do (because the game is almost impossible for anyone but the original developers to actually beat). The scrolling printout on the screen should probably be made faster, and the message that you can only carry 3 items needs to be a *lot* faster, because it is totally frustrating the way that it is.
Those changes, and whatever-else the developer who was porting it wanted to add, would provide an improved game on the Enterprise, and so be worth doing.
For Renegade, the obvious thing to add is the horizontal scrolling that had to be dropped on the Amstrad because the machine couldn't do it in hardware, and it was too slow to do it in software. With an Enterprise 128 you have twice the memory of the Amstrad 464 that the game was targeted for, and plenty of memory available to do double-buffered hardware scrolling.
Again, this would make an important visual improvement to the Enterprise version, and so make it worth doing, and also show the power of the Enterprise's hardware.
For Gryzor ... that it the one that I'd be the most intrigued to see on the Enterprise, because it would be possible to both add scrolling to the game, and probably also to add the extra stages from the NES version of the game. However, that is a project that I would want to do myself. I don't have an Enterprise anymore for testing, but I'd develop the game in ep128emu anyway, just to retain sane assembly times.
Anyway ... I'm new here, and you don't know me, but similarly I also don't know you, and I don't know about your programming capabilities and interests.
May I ask what games and/or other Enterprise programming you have done?