As stated above: your house, your rules.

There are two ways I would set this up. One is to have the grapple be an 'on hit' rider. In this scenario I would have a strength save to resist, DC 8+prof+(str or dex). This is superior on action economy but easier to resist/escape.

Alternatively if the grapple replaces an attack and deals no damage then use athletics as normal, with all the possible expertise advantage and other boosts that go with it. The real benefit is grapple at reach can completely lock down a target without reach or range.

In either case the +1 won't make a huge impact. I would probably allow it.