Opinion
Agree; Disagree; Erm...; I have no clue
I'm totally in favour/against it
Completely opposed/agree
Good idea in theory but not in practise
I have some major doubts
Some slight reservation
Complements
I am glad you asked
That is a good/great question
That question is rather interesting
Concerns
I am quite sure
I am not 100% confident
That has caught me off guard
Softeners
Frankly speaking
To be completely honest
To put it bluntly
I don't know
I am not the best person to answer that
I am not sure to hazard a guess
That falls beyond my scope of expertise
I don't think I can answer that
It's anybody's guess, really
I don't know where I stand, really
Mitigation
I would like to research that topic
It can take a few minutes to formulate the answer
Let me consult with my ...
I'm sure I'll be able to sort it out
Rough answer
Here is what I can tell you
My rough estimation would be
Let me put it like that
My best guess would be