Help with Home Door Intercom Upgrade Please

Hi,
I was wondering if someone can help me with replacing my existing intercom system. Please see attached pictures. The issue is that the buttons have to be pushed very hard for the bell to work and the speaker and microphone don't always work.

There are two outside door entry stations:
1) Ground floor with one button (not pictured, too rusted).
2) Front door with three buttons for Ground, Floor 1 and Floor 2 (pictured).

There are three inside stations. Each of the 3 floors has an inside intercom station with a speaker and three push keys for talk, listen and door release:

1) Ground floor inside station can attend to both outside stations and door releases.
2) Floor 1 and Floor 2 attend to the outside Front door station and door release.

Ideally, I would like to upgrade to something more modern, maybe even with a built in camera, but I definitely do not want to rewire. What are my options?

Secondly, if I decide to replace with the same basic type of system but a different company, can I reuse the amps and door control unit?

Many Thanks

EDIT: Sorry the upload seemed to have rotated my photos out of alignment.

 

The main current wired brands are mostly Aiphone: Products - Aiphone

There are a fair number of wireless options (you can use the existing wired harness just to provide power).