As a suggestion, in relation to having two TA's.
If the Safir Model is selected, this will have a Fixed Headshell and leave the situation where wanting to trial out Cart's or have a collection of Cart's at hand to use, is presenting a precarious and risky situation each time a Cart' is to be swapped out.
A second TA worthwhile considering is one that has a Removable Headshell, but even more importantly, a design that has a very rigid secured method put in place for the Head shells attachment. A interference Fit design is the way to go.
As a secondary consideration, a Headshell Design that fits the above and is also available in a variety of materials.
With this type of TA in use, the Headshell can be pre mounted with a Cart' which is then aligned. Once in this condition, it can be kept in a Cart' Keeper. This is how I am doing it for myself.
The specific changes required between Cart's for the TA to undergo during Cart' Alignment can be recorded. This as a method will enable Cart's to be pre-mounted onto a particular Headshell type and put into service as a very low risk operation and easy to achieve method.
It will certainly leave the main TA un-tampered with, keeping in place the critical adjustments that have been carefully added during the periods spent making discoveries, in conjunction with the Cart' of Choice.
As you are expressing an interest in having Two Phon's as well, the method will also enable speedy setting up of exchanges, to create the initial impact of the changes being made to not incur too much delay during the comparisons.