I agree - you certainly aren't being over-cautious.
To some extent, you are constrained in pilot experience by who you have available. The best pilots for the job are likely to be amongst your most experienced, but ideally those with some reasonable technical literacy - any ex-maintainers or science graduates in that lot? It's unlikely that any "normal" pilot will automatically know how to fly a test schedule and some training will be needed - you might do worse than bring in an experienced flight tester to help you put a training course together. Once up and running, you may hopefully be able to do most required ongoing training in-house with the expertise you will then be building up.
It is worth also thinking in terms of not relying solely upon your pilot for the air test, particulary since you're apparently looking at fairly complex multi-seat aircraft. If you involve some of your most experienced maintenance crew-chiefs and pair them with the pilots being used, flying them together this may work much better for the air tests than normal flight deck crew only (if you still have flight engineers on any of your aircraft on the other hand - they're probably the best people in this role.)
Weather conditions is something that you need to decide locally, but it's likely that you won't wish to do the main part of any air tests in IMC; day-VMC conditions are pretty much a global normal for most test flying, and would be a sensible starting point since you are then not absolutely reliant upon many of the avionics which may well be at the core of your air test, and also aircrew capacity (otherwise used otherwise in instrument flying) is freed up to concentrate upon the air test.
A few additional thoughts. Absolutely create standardised procedures, and whilst you can't standardise the test schedule you would be well advised to standardise the format and ensure formal document control, making life much easier for everybody in the process to keep tabs on what they're being asked to do for any test. Again, this standardisation reduces the risk of anything being missed, and also frees up everybody's mental capacity to concentrate their skills and intellect upon the air test. If you have a small number of home operating bases, again define "usual" test areas, well known to the crews, for exactly the same reasons. That said - don't write the procedures too tightly - give yourselves some reasonable operating flexibility or your entirely sensible desire to improve the organisation's safety may inadvertently ramp on costs and complexity, to the detrement of the main operations.
Best of luck.
G