I don’t know if this is a solution you’re interested in.
I’ve been wanting to purchase the Altman latches and retain the exterior/interior handles and function in and out but also planning to install keyless push button start that also is Alarm and locks and unlocks the car as you walk away from and to it like a modern car. Has other functions options as well, such as turning on the lights as you walk up to it.
this company seems to have a good reputation and has 20% off Black Friday for Thanksgiving.
don’t know about reputation or if anyone has used their system. Seems like $502,000 range -20%?
http://digitalguarddawg.com/