[Griefbringer]

The easiest option would be to diable the option to "sell" platoons on the purchase screen, unless you sell their company HQ first. However, this would also reduce flexibility for various legitimate purchasing techniques which involve buying a company, selling one of the platoons and then buying another one as replacement (eg. substituting one of the platoons on a mech infantry company with tanks).

Another option would be to not make any changes to the purchasing rules, but instead make players pay extra for their company commanders. Currently, the company commanders cost the same as any other similar unit in their formation. How about making them cost say +25 points extra for their abilities?