Just as a matter of interest, not because I can help, are you used to running 120 miles/week up hill and down vale in all weathers? Would you think it was cheating to discard stuff along the way and buy new?
How about leaving your stuff in the morning and going back by bus to collect it after the run?
Can't give you a good answer but can share my experience.
My trail shoes have more grip on mud, sufficiently so that I can run confidently where in ordinary shoes I'd be going very gently, but they give a slightly hard ride on roads. I've only regretted wearing trail shoes where my navigation skills have failed and I've chosen roads instead of planned trails.
What do other people at your parkrun do?
What are your particular fears about wearing trail shoes on roads?