tl;dr; KB should not enter a pre-election alliance with Reform and I am verbose about it, sorry all, got carried away.
I am all for Kemi Badenoch talking, listening and trying to appeal to Reform voters (to an extent), but she should not enter an alliance with Reform before the election.
First and foremost, Farage is too polarising. If there was a pre-election agreement, I could well imagine Labour, all the loony left and the national parties deciding to go for a maxi-coalition "All against the right, Reform and the Tories!". They are usually crap at working together (looking at you, Your Party) but to give a rubbing to Nigel and their ancestral enemy, the Conservatives, they could well pull it off.
And Reform is not in its best shape, the wind is a bit out of their sails, they seem to have plateau'd and not been able to turn support into enough seats. Nigel got all stroppy and threw his toys out of the pram about his 5mil and Posh George, he is in a mess of a byelection against a selection of weirdos in dress up costumes ordered from Temu (sorry, Count Binface, a part of me still loves you), with an ongoing investigation that will pop its head in the near future. And I don't think he wants to be PM for real.
And who wants to share power with Nigel Farage? Because that never ends well for those who have tried, thoughts to Rupert and many others.
She does not need the aggro while she looks more and more every day like the strong, confident, resolute one on the right, who REALLY wants to be in charge and more than ready to do the tough jobs, not just a protest vote and a diatribe while clutching a pint and a fag.
Her star is rising, she is hitting the right note in terms of image and message, right where voters are even if they don't know or admit it yet, more centre-right than Labour/Lib Dems, showing clearly that the "progressive" stronghold over policy and culture will stop with her, yet not Nigel, more respectable than Reform and its shady foreign/crypto money, more traditionally British than their US-style politics, less excessive/racist/xenophobic, more professional and able to get things done in Whitehall than the Reform newbies.
She would lose all this appeal with an alliance. It's a much bigger pool of potential voters to alienate than the people on the right who are ok with Farage and his ideas but for some reason will downgrade to voting for the Tories.
Her biggest issue is still the Tory legacy. But she has recently taken the right steps in that direction too. Her speech last week was very good in that effect.
But after a GE, depending on the results, it would be something else...