Ainsley Maitland-Niles has three options for a loan move on deadline day, one of which could include an obligation to buy.

The Athletic report that after days of negotiations, Ainsley Maitland-Niles will settle his future ‘in the coming hours’. The expectation is that he’ll leave on loan, and it’s just a matter of choosing a club at this stage.
West Brom are off the table, with Arsenal not wanting him to go there. Newcastle United are still in the mix, but right now they’re an ‘outside possibility’. That leaves Southampton and Leicester City as the leading contenders.
Arsenal prefer Southampton, as the club want Maitland-Niles as a full-back option. The player wants Leicester City, as they’d give him the chance to play in midfield.
Leicester want an option to buy in Maitland-Niles’ contract, but Arsenal would prefer it was an obligation to buy, which Southampton would consider.
Obviously, if Arsenal include an obligation to buy, it no longer matters where the loaning club play Maitland-Niles. But since Leicester City aren’t including one, their preference to use him in midfield is a problem.
One other problem is that Leicester City are still in the Europa League. If Arsenal loan them Maitland-Niles, they could end up facing their own player later in the knockout stages.
That’s allowed, as we’ve seen with Philippe Coutinho facing Barcelona in the Champions League last season, among plenty of other examples (Courtois vs Chelsea, James vs Real Madrid, and so on).
You can see why Arsenal are going to push the Southampton option if it’s up to them. We should know more as deadline day progresses.