Blend frames but not change speed of clip

Hi
I have plans to film a ceremony soon in 4k on a tipod.
My camera only does 25fps in 4k and everything looks fine except that little stuttering I see when people walk even slowly across from left to right for example.
How can I create new frames to try and make the motion smooth and then perhaps export into 30fps with some frame blending?

I tried to start with a project timeline using 30p, dragged down the 25 and in the project settings still said 30p and export screen said 30p but there was no change in smoother people motion. The "speedometer icon" where I can change video quality and use optical flow etc was greyed out for some reson also above the timeline.
Is this option only available when I conform equally, i.e. 25 to 50fps, 60 to 30 etc... ?

You do know that many people see 25p (or 24p respectively) as a gold standard for a cinematic look? I don't want to smart ass around. Just sayin because sometimes as an editor one pays too much attention or spends too much work on something that might not be necessary a all. Why have all the hassle if it's not really necessary?

yep
But I just now tried with my iphone 6 doing the same walk-by-the-frame myself. It saves default as 30fps according to VLC.
Yes the video is much noisier but my body moves more natural to my eyes on 30fps compared to 25.
Hmm.. maybe this is because of rolling shutter on the full frame sensor or something, have to try 50fps to check for sure.
Either way it would be nice to somehow add some effect to any of my 25fps source material to make it look smoother, I dont mind exporting it to another framrate, it will probably just be on youtube or sent within some mp4 file or so but I as I mentioned I don´t want to change the clip speed.

Frame bleeding is a classic feature of Adobe After Effects. I am not at my work Mac so I can't open Motion to see if that's an option. You can often simulate frame blending with time effects that stickup adjacent frames. Different type of look, though.

I recently worked with davinci resolve, it sucks the life of my machine but at least it has some export options to blend frames and stuff like that, sometimes FCP seems a bit too beginner friendly.