I’m not sure if you are asking to replace the feeling, or add RPE on top, because I don’t see the point in adding RPE, my arguments :
the “feeling” rating is useful in the way that effort does not match feeling, i’ve done plenty of zone 2 training where i felt like shit, thus despite the low RPE, low feeling, which is very useful for the recovery analysis
RPE can (and is) be calculated from heart rate (and infered FTP zones), and Suunto app already provide PTE, which looks a lot like RPE, so maybe it’s just about changing the PTE to match RPE ?
user experience wise, a 10 point scale that people have to fill is generally to be avoided because people have great troubles staying consistent in such a fine scale (and I agree with that statement personally), thus a 5 point scaling (like the smileys) is usually preferable.
But indeed that It would be great to be able to edit feeling afterward as sometimes the immediate feeling (happy, full of adrenaline and endorphins) doesn’t match the actual feeling (a creaking knee ^^)