Multiple Virus Scanners: AEC Trustport: Similar freeware: Help

I ran into an article which mentioned AEC Trustport in Informationb
Week, how it allowed for several virus search engines to work without
conflicts. The trustport platform licenced other anti-virus engines
to work in this wise: one was going real time, and others were going
on demand. Generally the received wisdom is that virus scans conflict
with one another and the system is at best a hash and at worst a
crash. Trustport has a platform to remove this issue.
I contacted their support and requested a freeware version. No-
go, they do not have one, have no plans to make one. Fine, but here
are my questions:
(1) is there software which would allow me to use a software "toggle
switch" so to speak, and turn on a real time virs scanner and at the
same time turn off an on demand virus scanner, maybe several of them?;
(2) is there any rare or obsolete freeware which will allow the use of
more than one virus scan?
Yes, some will say, they get along fine with three, but I
disagree. Could anyone advise me of how to get, say, AVG and Zone
Alarm and some others, all freeware virus scans, to coexist and not
conflict on my PC, if I run them--NOT concurrently, but in
succession. Maybe,hypothetically, AVG virus scan as a real time
scanner and Zone Alarm on demand, and two others on demand,
hypothetically. Then maybe I want to make Zone Alarm the real time
scanner, etc. etc. Got the idea?
Someone please advise or help if you have the freeware to do it.
I thank you very much.
Robb