Ok, it has been a long and difficult operation, but I understood something about the F1 88 mod files.
1) It's possible to do the pit with all the cars of the mod, even with the Coloni, but you DON't have to assign ANY botton for "starter" nor "ignition". Without setting these bottons, when the pit table appears, you push enter as usual, and the car switch off its engine after 2/3 seconds. When the pit crew has finished its work, your Engine will switch on automatically again, and you will able to restart from the pit. This procedure works in the same way even for all the other cars.
2) Otherwise with all the other cars (except Coloni), you can assign the "IGNITION" button (with the "starter" you can only switch on your engine, but you can't switch it off), to switch on/off your engine, but it works ONLY in the pit lane. So, if you drive with manual clutch and for some reason, your engine will stall during a lap outside the pit lane, your race is OVER. Assigning the "ignition" button, will let you save some time during the pitting procedure, because you can switch off the engine before arriving in your pit place, and the refueling will start immediately after you pushed Enter. At the same time when the refuel is complete, you can immediately switch on your engine, even during the tyre change (admitting that you have to change your tyres)... Sooner you switch on your engine after the refuel is complete, and sooner you will leave the pit, with another slightly time advantage than the automatic switch on procedure (illustrated at the point 1)).
3) I've looked into the ".eng" files of the mod, and the only way I found to solve this trouble is to change this string into the "88Coswoth DFZ.eng" (Coloni engine file): OnboardStarter=1 // whether vehicle restarts when stalled. (The Default value is 0 for every .eng files of the mod)
Changing this string in every file ".eng" of the mod, will allow to use the "ignition" button when you want, even if your engine has stalled during a lap. This is an "advantage" for the people that use the manual clutch I know, but it's one of the 2 ways to make equal the Coloni and the rest of the field in terms of time pitting procedure. The other way would be to change the "Coloni.hdv" file and make it point to another ."eng" file (for example to the "88CosworthDFR.eng").
4) I remember that someone created a new "specialfx.tec" file for the F188 mod to solve the "bumpy" cars problem. I downloaded and tried it, and it works pretty good for this mod. I uploaded it on humyo, if you want to try it
http://www.humyo.com/FCrSYMC/specialfx.tec?a=dt64VuCXgBo (Install it into GTR2/GameData/Location folder. Remember to make a backup copy of the original one
5) One year ago, an Italian guy "revisited" the car physic of this mod, and we tried it in a fun event. In my opinion it was a lot better than the original, but he changed a bit the engine power to make the car performance closer than the original engine files of the mod. If you want to try it, that's the download link:
http://downloads.italianracers.it/Gtr2/Mods/F1_88_by_cacioppo.7z. If you like more the physics of this new one, I could rearrange it with the original engine files, leaving only the new physics.
In every case, it would be a simple operation to make some changes to this mod. I can make a self-extractor file with WinRar, and everybody can easily change the files. I used to do it when we've organized the Nordschleife VDA event with the P&G, and it worked pretty well for the UKP&G people who joined our race. If you need the original files, it's enoguh to make another self-extractor for the files we're going to change (in the case we will).
Sorry for the lenght of the discussion
I hope to have provided some good points. Cu