Straight cut gears are of not a performance thing and many old type gearbox replacement sets where straight cut. I don't think dogboxes are a problem as long as they are H pattern.

i beleive the intent here was to keep with production type gearboxes, but give some freedom to change them. that was seen as the lowest possible cost option , giving people wanting to race cars with particualrly fragile boxes, an option to upgrade somewhat., but not break the bank in doing so.   Dog engaged, straight cut however, are always in the realm of expensive, and there is no doubt dog engagement boxes give faster changes in the right hands. BUT, they are expensive to maintain (ive done  quite  few over the decades).   A few really popular models from this time period will still be able to buy off-the-shelf close ratio helical syncronised gear sets (Toyota etc) , but that wont be an option for everyone.  In Mitsubishi land for example, this is almost unheard of and just about the only affordable option is to move up to the next "model" (larger) gearbox in their range. In some cases, this is dead easy to do as they literally bolt on. Of course, this rarely helps with ratios, but at least the fragile box is gone and people can concentrate on improving themselves, not forever fixing the car

I feel no dog-engagement is a reasonable proposal. Straight-cut synchro gear sets should be acceptable. What about 'uprated gearboxes' having to be from the same manufacturer as the car - thoughts? Another method of simplification and cost control.