Bear in mind that at TXL every gate has the check in counter right beside it at least at the A gates which TAP use so you will be seen by the check in staff. Then every gate also has it's own security where the staff are generally quite helpful - moreso than say FRA but it is Germany and rules are rules. You are taking a chance. If you are a *G in business then you should have a three piece allowance anyway so check in of any or all of it should cost you nothing.
Also at TXL the *G lounge is the LH SEN lounge which is a landside lounge, upstairs from the entrance by gate A0/B1. You need to leave it at least 30 mins before departure time in order to clear security at the gate. Once in the gate area there is little or nothing other than the odd duty free shop and a lot of hard seats.