I don't usually correspond via e-mail as I prefer to answer any questions in the forum, that way other people can add their input along with mine.
I'm happy to help as best I can, if you don't mind I have copied part of your e-mail below and will answer them here.
"If one had two distinct plants growing in a same hydroponic system with the
other one being vegging plant and other one being a blooming plant how should
the nutrients be set."
First off, it's best practice to grow veg and fruiting plants separate, as you've read. If you absolutely must grow both together then you should dose for fruiting as the vegging phase has a higher nitrogen content, this won't be beneficial to growing fruit - in fact it may interfere with the fruiting process; peppers, for one, don't like higher nitrogen. You should really separate both plants for optimum growth.
"All the sources I've read instruct different nutrient solutions for both
stages (veg and bloom) but the setup of the system would benefit from mutual
If one would maintain say transition stage nutrient solution (GH Flora), how
would the plants develop?"
One of the main problems here is the EC level, if you were to grow say tomatoes and lettuce in the same system you would have to give the toms a higher EC for growth, this will cause major problems for your lettuce; leaf burn, bitterness... Sticking in the 'transition phase' is not really ideal in my opinion, whilst I've never done it myself I cannot comment on the outcome - I could guess that your lettuce will suffer from burn etc., and your fruiting plants will suffer from retarded fruit development (lots of vegetative growth as opposed to fruit production), but, as I say, I cannot substantiate this.
"What is your opinion about the effects of this type of nutrient solution e.g
smaller flowers, stunted growth etc?"
Any plant not fed the ideal nutrient for 'it' will suffer, you are talking slower development, malnutrition and the problems associated with over feeding...
"If the transition stage solution is not the preferable which kind of solution
The preferable way would be to separate both plants and feed them what they require individually. Remember here that the pH is also important, different plants require different pH's, do your plants have the same requirements?
I'm going to have to say I cannot recommend a solution that does it all, I don't think there is one on the market, or that your could mix, that would do the job of growing both plants together successfully? Most are either 2-part veg and bloom stages or 3-part stages that require mixing to your plant type.
If it were me, I'd grow then apart. If you cannot, then I'd decide what plant you would prefer to grow and feed for that plant - the other plant will likely suffer though.
I hope this helps.